Geolocation based push notification

I'd like to push an alert to my iPhone users that are within a geographic range. I can get their location when my app is "alive," but not otherwise. Would a good approach be: send the localized alert based on users that appeared "in-range" in the last hour? Otherwise, I'm not sure how to only alert relevant users. Is th开发者_如何学Pythonere a smarter approach?

The lack of background processing really hurts applications like this. I think your solution is probably the best approach, given that rather severe limitation. However, you definitely should offer the ability to tone this down, as it could start to get really annoying.