Just to add even if at this point it might not be related. I reinstalled the app, and now it does seem to close when i leave the car, however it just crashes completely.

I can confirm this too on Lollipop. Unless I go and press stop, the stream persists although the music actually seems to stop.

I have the same problem with AOKP running ICS. Switching the stream to FFMpeg resolves this particular issue.
Is there any advantage using Android instead of FFMpeg?