Use APKPure App
Get RIOT OS Bluetooth Shell old version APK for Android
Connect to the BLE shell of RIOT OS
This app gives you a terminal for the RIOT shell. The stdio module is implemented with NimBLE on RIOT side. Have a look at the RIOT project on github: https://github.com/RIOT-OS/RIOT
See https://github.com/HendrikVE/RiotBleShellApp for the source code of this app.