Send GPS coords when the app is minimized (iPhone)

I want to build an app that is checking the current user GPS coords and send it to the server when the server asks for it. Is it possible at all to do this when the app is minimized?

How can I implemen开发者_JS百科t a service like this? It should be real-time:

The server asks for users locations --> The clients are sending their current location --> The server processing their location --> The server is sending to X of them a notification.

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Take a look at http://developer.apple.com/library/ios/#documentation/UserExperience/Conceptual/LocationAwarenessPG/CoreLocation/CoreLocation.html#//apple_ref/doc/uid/TP40009497-CH2-SW10