Fire up GPS when app is launched?

Since GPS takes a few moments to lock-on, it would be prudent to fire up the GPS when the app is started instead of when "Start Recording" is pressed.

But, this has battery implications. Need to figure out if this can "time out" after a minute (or some period) if user is just looking at old trips or goes back to home screen.

Maybe it can fire up the GPS when the main screen is foreground, but shut off if it goes background AND there are no current trips being recorded.