Can GPS data be sent from the iPhone while App is running in memory/background

I'm looking to put together an app that will figure out other iPhone use开发者_如何学编程rs in the same area.

I'm curious as to know if it is possible that an app can run in the iPhone memory or in the background and send push notifications to the owner of the phone when someone with the same app is in the area.

I gather I can do this if the App is actively turned on, but am wondering if this is possible say if the users phone is in his pocket for example.