The basics:

• Android BLE tutorial (official)
• Ultimate guide for Android — this is excellent and well worth the read
• an excellent tutorial on Android BLE

stay connected and reestablish connection even in background

iOS

author: Stefan Walkner

requires a separate chip that only advertises

some gotchas for multiple devices?

• how to turn on/off iBeacon advertising when multiple devices are involved?

Android

• Android Beacon Library
• will it work with iBeacon?
• The Beacon library was initially created before Android 5. Is the beacon library still required or is this built into Android the way it is built into iOS?

Running tasks in background:

• React Native Queue: can execute only 1x every 15 minutes
• React Native Background Task: also limited to 1x every 15 minutes
• Headless JS is what is used for running React Native stuff in the background, but it might only support Android

Beacons:

this mention of indications in react-native-ble-plx suggests beacons can receive information back (2-way communication)

• React Native BLE plx tutorial

Expo: a React Native with components and everything you need built-in

• using with BLE (having to detach)

Misc:

• getting tile button to work with a Mac