HAMMER (Handheld Acoustic Modem for Mobile Exchanges with Radios), also referred to as ARIK, is an acoustic modem plugin for the Android Team Awareness Kit (ATAK) that allows ATAK devices to communicate with each other over any voice-comms radio (e.g., via a walkie talkie).
Pre-built, signed versions of the plugin are available on the takmaps site.
This source code was approved for public release on October 7, 2020 via case number 88ABW-2020-3096. A copyright of the public release notification is included in the repository.