Maven by GM is like this. It's a little bit clumsy at times[1], but it does the job for hourly rentals (the primary purpose of the app). The cars have Android/iOS chargers in them. As far as I can tell, you would be in quite a bit of trouble if you ran out of battery.
[1] If the internet connection is weak, it will attempt to update trip information before letting you unlock the car. You're better off turning on airplane mode.
[1] If the internet connection is weak, it will attempt to update trip information before letting you unlock the car. You're better off turning on airplane mode.