A few users have written in concerned about the GPS stopping in the middle of tracking a trip. Turns out they hadn't saved the trip before driving away. We're working on devising a more intuitive UI, but wanted to help users understand the intended way to use MileBug to get the most out of it.
When you add a trip and turn on GPS, you actually need to return to the Add Trip screen and save the trip for the GPS to continue tracking. The incomplete/ongoing trip will appear in red in the Trips List while the GPS continues to track in the background. When you arrive at your destination, simply tap the red trip and stop the GPS tracking. The end odometer reading will be filled in automatically with the totals added to your mileage log.
Remember: Save the newly added trip to have the GPS continue tracking.