This doesn't use your GPS.
It will use cell tower/Wifi triangulation, because the EXACT location isn't impotrant, it just needs a rough location.
So battery life won't be effected.
Same with location based reminders, 99% of the time it uses cell tower/Wifi triangulation, and when it knows your are close to your target destination, only then the GPS will kick in the pin point where you are.
This is why location based reminders don't take up much battery at all