A simple solution could be : - Apple has a limited set of "actions" that third party app can "suscribe" to ("checkin", "reminder", ...), like there is a limite

A simple solution could be : - Apple has a limited set of "actions" that third party app can "suscribe" to ("checkin", "reminder", ...), like there is a limited set of multitasking capabilities - Limit the number of Application that "suscribe" to an action (i.e: only 4 apps can checkin, if another app wants to suscribe, display a warning to the user so he disable other apps in settings, like for notifications) - Prompt the user the first time "Where would you like to checkin", and remember the choice for future checkins. The user can also specify ("Check me in" - "I will check you in using Foursquare at ..." - "Use Facebook Places")