How it should work (for now): 1. Start application from terminal 2. Make a call, when call is picked up, fm transmitter is automatically started and sound is automatically routed through the fm-transmitter. OR Wait for a call, when the call is coming the fm-transmitter is started, and when the call is active (answered by you) the sound is routed through the activated fm-transmitter. No need to press the speaker button, the sound is possibily re-routed on the normal way again. I haven't tested it yet witouth the patched version of fmtxd (usr/sbin/fmtxd) as described by qwerty12: The patch will be implemented in the next version so you can toggle the patch from a gui.