El Bracer — forearm EMG wearable
A forearm-worn device that reads EMG and motion, classifies it on-device, and streams the result to a phone. Many iterations, three radios, one very patient enclosure design.
- Sensing
- Surface EMG + accelerometry (forearm)
- Firmware
- C++ — filtering and on-device classification
- Link
- BLE (previously Wi-Fi, then Bluetooth)
- Feedback
- Haptic cues · battery monitoring
- Client
- iOS app
- Context
- HALO — Unbabel Labs
Part of the HALO / Unbabel Labs work on silently controlled interfaces. El Bracer is the forearm unit: it senses muscle activity and movement, decides what the wearer is doing, and hands that to an iOS app.
What’s in it
- Sensing: surface EMG plus accelerometry from the forearm.
- Firmware (C++): filtering and classification on the device itself, plus an auto-reconnect protocol so a dropped BLE link recovers without user action.
- Feedback: haptic cues and battery-level monitoring.
- Radio, over time: started on Wi-Fi, moved to Bluetooth, now BLE.
Iterations
The device has been through many revisions, and several alternative form factors were built to suit different tasks. Prototyping spanned textiles and sewing, FDM and resin printing, and PCB work. It has been demonstrated publicly on the Web Summit main stage and at the UN “AI for Good” summit in Geneva.