Happy to report that while I can't say 100% for certain yet this issue is completely solved on the beta stream, progress is being made. The root cause has definitely been identified; apparently Motorola phones don't report battery statistics correctly (or at least normally compared to other phones) in Android. The dev had found an undocumented workaround previously which worked up till now, but something in the JB update for this phone changed things. When I sent him log files to review, he discovered that the phone wasn't reporting to the app properly in 10% increments, but rather over a 20 second period it reported 70, then 100, then -14 percent (weird I know).
He put out a new update on the beta stream the next day, and after I had a ~50 minute work road trip to another office that I tested with (and I made a point to have bluetooth on even though I didn't have another device to pair to), the mapping process didn't halt during that frame of time. My Friday trip 9-10 hour drive to PA will be the true litmus test, but if nothing else, this is definitely progress!