WhisperTag
nRF52840 · Zephyr RTOS · KiCad · BLE · Kotlin · Swift · NestJS · Next.js
WhisperTag is an early-stage hardware product: a wearable BLE device that lets children whose phones are locked away at school send voice messages to their parents. The trick is that the device has no SIM - it relays opportunistically through nearby phones running the companion app.
It is the widest-spanning thing I have built: nRF52840 firmware on Zephyr RTOS, a KiCad-designed PCB with a Fusion-modelled case, native Kotlin and iOS relay apps, a NestJS backend and a Next.js parent panel. Still in its first phase, but every layer of the stack - silicon to cloud - is mine.
Highlights
- Firmware (Zephyr/nRF52840), PCB (KiCad) and enclosure designed in-house
- SIM-less messaging via BLE relay through nearby companion phones
- Native Kotlin + iOS relay apps, NestJS backend, Next.js panel