I have two suggestions in regards to the batteries.

1. This is more towards emulators and the developers for them. If you could include an icon that comes up when the battery gets low, it would be a lot easier to gauge on whether we should just save and charge it or keep playing. I just had the device shut down on me in the middle of a very difficult part in the game ALMOST to completion, thus causing me to lose all of that progress.

2. It'd be nice to have some sort of time left on the device (provided that it's able to calculate from full the empty charge) based on the average expectations of the device. I can accept if it's off by a little bit but it would give some peace of mind when playing the device to know that there is two hours left, so another hour or so would be safe to play.