docs(connectors): survey voice wearables for the next connector

docs/connectors/wearable-survey.md

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+# Voice wearable survey: choosing the next connector
+
+Survey for [#13](https://github.com/october-dev/murmur/issues/13), checked on **2026-09-25**. It compares voice
+wearables and open hardware as candidates for Murmur's next connector after Omi, and recommends one.
+
+This is desk research from vendor pages, official SDK and protocol documentation, and repositories and their
+`LICENSE` files. No hardware was bought or tested, and no closed protocol was examined. Availability changes quickly:
+Limitless stopped selling its Pendant to new customers after its acquisition, and Brilliant Labs replaced Frame with
+Halo in its official store. Re-check any row before starting implementation. Repository activity below is as of the
+survey date.
+
+**Evidence labels**
+
+- **D**: documented in a primary source (vendor site, official docs, SDK repository, package registry, or `LICENSE`
+  file), linked in the row or the notes.
+- **R**: reported by secondary sources (for example news coverage of an acquisition), not confirmed on a vendor page.
+- **U**: not confirmed from a primary source during this survey. Treat it as an open question, not as a limitation or a
+  capability.
+- **Inference**: a conclusion drawn from documented facts, stated as such.
+
+## Summary
+
+| Candidate | Buy new today | Transport | Third-party live audio | SDK / code license | Vendor account or cloud needed | Verdict |
+| --- | --- | --- | --- | --- | --- | --- |
+| Omi (baseline) | Yes (D) | BLE (D) | Yes: BLE audio service; Opus 16 kHz default, PCM and µ-law 8/16 kHz (D) | MIT (D) | U | Current connector |
+| **Mentra Live** | Yes, US retail only (D) | BLE and Wi-Fi (D) | Yes: Mentra Bluetooth SDK `mic_pcm` (16 kHz, 16-bit, mono) and `mic_lc3` events (D) | Apache-2.0 SDK source and Android/iOS packages; npm package metadata says MIT (D) | No: works offline without Mentra-hosted cloud (D) | **Recommended** |
+| Brilliant Labs Halo | Yes, shipments began early August (D) | BLE (D) | U: LE-Audio-style voice pipeline mentioned, no third-party stream documented | SDK BSD-3-Clause (D); firmware mixed, incl. restrictive Alif SDK license (D) | No: pairing and self-flashed OTA firmware (D) | Runner-up |
+| Even Realities G1/G2 | G2 yes; G1 U | BLE (D) | G2 microphone events through the Mentra Bluetooth SDK (D); G1 U | Official Even Hub SDK license U | U | Reach G2 through the Mentra SDK |
+| Plaud NotePin | Yes (D) | BLE (D) | PCM via `blePcmData` during recording and sync (D); general-purpose live capture U | Sample app Apache-2.0, **SDK binaries proprietary** (D) | Yes: per-user JWT from the vendor (D) | Not recommended |
+| Limitless Pendant | No: sales to new customers stopped after acquisition (R) | Cloud export (D) | No live stream; post-hoc Ogg Opus export via REST (D) | No public SDK or code license found (U) | Yes: API key (D) | Excluded |
+| Bee | Yes, $49.99 from Amazon (D) | U | No raw audio; processed data only (D) | U | Yes: vendor login (D) | Excluded |
+| OpenGlass | N/A: superseded (D) | BLE (D) | Superseded | MIT (D) | No | Merged into Omi (D) |
+| DIY XIAO ESP32-S3 pendant | No product; open designs only (D) | BLE (Owl) / Wi-Fi (xiaozhi) (D) | Yes, the builder controls the firmware (D) | MIT (D) | No | No maintained wearable design |
+
+## Candidates
+
+### Omi (baseline)
+
+- **Audio (D):** BLE service `19B10000-E8F2-537E-4F6C-D104768A1214` with an audio data characteristic and a codec-type
+  characteristic. Supported: PCM 16/8 kHz, µ-law 16/8 kHz, and Opus 16 kHz, all mono. Opus has been the default since
+  firmware v1.0.3. [Protocol docs](https://docs.omi.me/doc/developer/Protocol)
+- **License (D):** MIT. [BasedHardware/omi](https://github.com/BasedHardware/omi), not archived.
+- **Availability (D):** Omi and DevKit models sold on [omi.me](https://www.omi.me/).
+- **Offline / BYOK:** U from primary docs. Inference: because the BLE protocol is documented, local capture does not
+  depend on the vendor cloud; this is how Murmur's connector works.
+
+### Mentra Live (recommended)
+
+- **Availability (D):** sold on the [vendor site](https://mentraglass.com/pages/live). "Retail website orders ship only
+  to addresses within the United States"; business orders outside the US go through Mentra support.
+- **Transport (D):** BLE and Wi-Fi.
+- **Integration path (D):** Mentra offers two SDKs.
+  - The Miniapp SDK (`session.mic.onAudioChunk()`) is beta. Its miniapps run on the phone inside the Mentra App, and
+    "there is currently no way to distribute a miniapp built with the Miniapp SDK".
+  - For Mentra Live, Mentra writes: "we recommend using the Mentra Bluetooth SDK", which connects an Android or iOS app
+    directly to the glasses. [Overview](https://docs.mentraglass.com/app-devs/getting-started/overview)
+  - A Murmur connector cannot live inside the Mentra App, so the **Bluetooth SDK** is the path.
+- **Audio (D):** with capture enabled, the Bluetooth SDK emits continuous `mic_pcm` events (`sampleRate` 16000,
+  `bitsPerSample` 16, `channels` 1) and, when enabled, `mic_lc3` events with frame duration, frame size, and bitrate.
+  [Audio guide](https://github.com/Mentra-Community/Mentra-Bluetooth-SDK-Starter-Kit/blob/main/docs/audio-guide.md),
+  [API reference](https://github.com/Mentra-Community/Mentra-Bluetooth-SDK-Starter-Kit/blob/main/docs/api-reference.md).
+  The BLE wire protocol is described in
+  [mentra-live-ble-wire-protocol.md](https://github.com/Mentra-Community/Mentra-Bluetooth-SDK-Starter-Kit/blob/main/docs/mentra-live-ble-wire-protocol.md).
+- **Account and cloud (D):** "Your software can control the camera, speakers, microphones, touchpad, and buttons, work
+  offline, and integrate without depending on Mentra-hosted cloud infrastructure."
+  ([Mentra Live](https://mentraglass.com/pages/live))
+- **Platforms (D):** Android (`com.mentraglass:bluetooth-sdk` on Maven Central), iOS 15.1+ (Swift package
+  [mentra-bluetooth-sdk-ios](https://github.com/Mentra-Community/mentra-bluetooth-sdk-ios)), and React Native / Expo
+  (`@mentra/bluetooth-sdk` on npm).
+  [Getting started](https://github.com/Mentra-Community/Mentra-Bluetooth-SDK-Starter-Kit/blob/main/docs/getting-started.md)
+- **License of the published SDK (D):**
+  - The SDK source is [`mobile/modules/bluetooth-sdk`](https://github.com/Mentra-Community/MentraOS/tree/dev/mobile/modules/bluetooth-sdk)
+    in MentraOS, whose `LICENSE` is Apache-2.0.
+  - The Maven Central POM for `com.mentraglass:bluetooth-sdk` declares Apache-2.0, and the iOS package repository is
+    Apache-2.0.
+  - The npm metadata for `@mentra/bluetooth-sdk` declares **MIT**, which disagrees with the source `LICENSE`. Both are
+    permissive and compatible with Apache-2.0, but the mismatch should be raised with Mentra.
+  - The Android module also bundles `lc3Lib` and `silero` components, whose licenses are U.
+- **Devices with microphones (D):** the SDK's
+  [hardware table](https://github.com/Mentra-Community/Mentra-Bluetooth-SDK-Starter-Kit/blob/main/docs/hardware-integration.md)
+  lists microphones on Mentra Live and G2 only. Other glasses supported by the Mentra App (G1, Vuzix Z100) are not
+  listed for the Bluetooth SDK, so their audio through it is U.
+- **Offline / BYOK:** offline operation is documented (above). Inference: because PCM reaches the app, BYOK or
+  on-device transcription is possible; Mentra also publishes an offline assistant example,
+  [Edge_AI_SmartGlasses](https://github.com/Mentra-Community/Edge_AI_SmartGlasses) (D).
+- **Background limits:** U.
+
+### Brilliant Labs Halo (runner-up)
+
+- **Availability (D):** Halo is sold on [brilliant.xyz](https://brilliant.xyz/products/halo) at $399; the page says
+  "shipments beginning in early August". The earlier Frame is no longer offered in the official store.
+- **Firmware (D):** [halo-firmware](https://github.com/brilliantlabsAR/halo-firmware) supports self-built firmware over
+  OTA with "no cable, no dev kit, no vendor tooling". Its README states the repository "is therefore *not* uniformly
+  Apache-2.0": Brilliant code is Apache-2.0 per file, but the vendored Alif Semiconductor SDK license "restricts use to
+  Alif silicon and forbids relicensing under copyleft terms". GitHub reports the license as `NOASSERTION`.
+- **SDK (D):** [brilliant_sdk](https://github.com/brilliantlabsAR/brilliant_sdk), BSD-3-Clause, Flutter, Python and
+  Web Bluetooth.
+- **Audio:** the README mentions "LE-Audio-style voice pipelines with on-device echo cancellation" (D), but documents no
+  third-party microphone stream (U).
+
+### Even Realities G1 / G2
+
+- The vendor's [G1 page](https://www.evenrealities.com/g1) currently leads to G2. G1 new-sale availability is U.
+- G2 microphone events are available through the Mentra Bluetooth SDK (D, hardware table above).
+- An Even Hub SDK for G2 is referenced publicly. Its microphone access and license terms are U; its documentation page
+  did not load during this survey.
+- Community BLE protocol notes for G1 exist, for example in [AGiXT/mobile](https://github.com/AGiXT/mobile). They are
+  reverse-engineered, not vendor documentation, and are out of scope under this issue's rules.
+
+### Plaud NotePin
+
+- **Availability (D):** sold on [plaud.ai](https://www.plaud.ai/products/plaud-notepin).
+- **SDK (D):** [plaud-sdk-public](https://github.com/Plaud-AI/plaud-sdk-public), iOS 14+ and Android 5.0+. The README
+  advertises "Real-time recording with live PCM waveform", and `blePcmData` "delivers decoded PCM (640 bytes, 16kHz
+  mono)". Whether PCM is available for general-purpose live capture outside Plaud's recording and sync flow is U.
+- **License (D):** the template app is Apache-2.0, but "the Plaud SDK binaries in the `sdk/` directory (iOS frameworks
+  and Android AAR) are proprietary and distributed under a separate license." A connector would depend on
+  closed binaries.
+- **Authentication (D):** a per-user JWT obtained through the vendor's partner API, plus separate developer-portal keys
+  for vendor transcription.
+
+### Limitless Pendant (excluded)
+
+- Meta's acquisition of Limitless and the end of Pendant sales to new customers were
+  [reported on 2025-12-05](https://techcrunch.com/2025/12/05/meta-acquires-ai-device-startup-limitless/) (R). The
+  vendor's developer page does not mention it.
+- The developer API is a cloud REST API with an `X-API-Key` header. Audio is exported after the fact as Ogg Opus, in
+  windows of up to two hours (D). [Developers](https://www.limitless.ai/developers)
+- No public SDK or code license was found (U).
+- Excluded: no longer sold new (R), and no live audio (D).
+
+### Bee (excluded)
+
+- The [vendor site](https://www.bee.computer/) sells Bee at $49.99 and carries Amazon branding (D).
+- The developer [proxy and CLI](https://docs.bee.computer/docs/proxy) expose processed data (facts, to-dos,
+  conversations, summaries) behind a vendor login (D). No raw or live audio is documented.
+- Excluded: no raw audio.
+
+### OpenGlass (superseded)
+
+- The [repository](https://github.com/BasedHardware/OpenGlass) states it moved into the Omi repository and is no longer
+  supported (D). MIT. The last push was 2025-09-22.
+
+### DIY XIAO ESP32-S3 Sense pendant
+
+- [OwlAIProject/Owl](https://github.com/OwlAIProject/Owl) (MIT) documents a XIAO ESP32-S3 Sense wearable over BLE (D),
+  but its last push was 2024-03-17.
+- [78/xiaozhi-esp32](https://github.com/78/xiaozhi-esp32) (MIT, with pushes in September 2026) is a maintained ESP32
+  voice assistant. It is Wi-Fi or cellular first and not a wearable reference design (D).
+- No maintained, BLE-first open pendant design was found. A DIY source is better served by Murmur's generic network or
+  local-audio connectors than by a device-specific one.
+
+## Recommendation: Mentra Live through the Mentra Bluetooth SDK
+
+Build the next connector for **Mentra Live** on the **Mentra Bluetooth SDK**, consuming its `mic_pcm` events (and
+optionally `mic_lc3`).
+
+**Why**
+
+- It is the only candidate besides Omi with a documented third-party microphone stream and a documented format.
+- It connects the app directly to the glasses and works offline without Mentra-hosted cloud, which matches Murmur's
+  local-first design.
+- Its SDK source and Android and iOS packages are Apache-2.0, the same license as Murmur. Halo's firmware (Alif SDK
+  terms) and Plaud's proprietary SDK binaries both fail this test.
+- The hardware is on sale today from an independent vendor.
+- The same SDK also exposes G2 microphones, so a second device may follow with little extra work.
+
+**Tradeoffs and risks**
+
+- **License details.** Confirm the licenses of the bundled `lc3Lib` and `silero` components, and ask Mentra to reconcile
+  the npm `MIT` metadata with the Apache-2.0 `LICENSE`.
+- **Codec.** PCM is 16 kHz, 16-bit mono. LC3 needs a decoder, so start with PCM and report the format through
+  `AudioFrame.format`.
+- **Glasses, not a pendant.** Capture posture, battery life and background behavior differ from Omi. Background limits
+  are U and need physical validation before the connector is marked supported.
+- **Availability.** Retail sales are US-only.
+- **Moving target.** Re-check availability and SDK APIs at implementation time.
+
+**Runner-up: Brilliant Labs Halo.** It is the most open hardware here: user-built firmware over OTA, BSD-3-Clause SDKs,
+and no vendor tooling. It becomes the better choice if Brilliant documents third-party microphone streaming and the
+Alif SDK terms are confirmed compatible with what Murmur would adapt. That is worth a follow-up question to the vendor.
+
+## Out of scope
+
+No hardware was purchased, no connector was implemented, and no closed protocol was reverse engineered. Community
+reverse-engineering notes are listed only to show they exist, not as sources.