[sevenless]

I don't have the game, but it sounds like GPS power drain is the big problem. Is there not some way to improve that? Maybe only turn on GPS intermittently and use accelerometers, wireless signals or the camera to track your position from the last known point and any landmarks?

[knowaveragejoe]

Just from using the app you can tell there are optimizations to be made that would dramatically save on battery life before even getting to the power draw from location services. Pokestops for example don't appear to locally cache their images and descriptions for long.

[fencepost]

Aside from the assorted obvious optimizations that people have discussed, it might be possible to "offload" the GPS to a separate battery-powered Bluetooth GPS receiver. I didn't see any results for this on a quick search, so I'm not sure whether it's been tested or not.

Of course, if you don't already have one a Bluetooth GPS receiver appears to cost at least 5x as much as a low-end external battery and 2-3x as much as a pretty substantial one.

[chatmasta]

I know iOS and Android already use non GPS data to aid in location sensing, but I'm not certain to which degree they actively avoid the actual GPS sensor.

[TorKlingberg]

Get a mobile power bank.