Phone's FM audio to Bluetooth or another output besides a wired headset or phone speaker?

For a FM transmitter to work in a phone, the phone needs a wired headset to be plugged in as an antenna.

The Android FM settings for audio output only allow wired headphones/headsets or the phone's speaker.  There is no way to get the audio output to a Bluetooth device.

It may not work, but you could try the following:

1) Look at the Widgets in the widget list for SoundAbout. Add the widget to your home screen named "Wired Mic Toggle".
2) Connect the other desired audio device (Bluetooth, HDMI..etc).
3) Plug in a wired headset, that also has a built-in microphone. The wired headset cable acts as the antenna.
4) I'm not sure if your phone will default to the wired headset. If so, open SoundAbout and change the "Media audio" setting to your desired output. "Bluetooth (A2DP) or ""Aux Digital (HDMI)"...etc.
5) One the Home screen, try pressing the Wired mic toggle widget so that it says "ON".
6) See if the FM app will now work and transmit audio to the desired audio output instead of the wired headset or phone speaker.