The source code for the ATAK Plugin which allows the communication of points/positions to be transmitted over analog/voice radios. The code allows transmission either by holding the phone to the speaker.
The code is liable to be useful as a guide post for how to write ATAK plugins, as well as for the off-grid TAK communication.
The plugin is not yet in the Play Store, but posting in the Google Play Store is in-process. There will be another post on CivTAK.org when the plugin appears in the Play Store.
You can find the source code posted here.