I'm going to start replying here, directly, or PM if you would prefer rather than at the Google+ group it's a mess there and hard to follow.
I've had to discontinue use of the app due to large increase in battery usage. I have to reboot my phone to reliably stop the extra usage of my battery and the increase always follows the use of Digital Car, if I reboot my phone and do not launch Digital Car my battery usage is as I expect for the day.
I haven't tested the compass yet but I do like the ability to disable and replace the built-in player with something else.
Also the setting screen is now a bit cramped and the text for screen settings are getting pushed behind the options below.