Core Location Alert API Proposal for iPhone SDK

Brady Forrest has a write up on how apple is missing a big chance by not allowing background apps because of the need for GPS updates. I think that he is right about Apple missing a chance, but I believe that the answer is not for Apple to allow background apps, but rather to create a new API for location alerting. I believe that this could be done in a way that is related to push notifications.

I'd suggest that applications might be able to register with a location handler and ask to be activated based on certain location events. I believe that this could be an extension of the core location services which are already exposed. I'd like to be able to ask the system to activate based on a least 3 kinds of events:

• Proximity to a point (given by coordinates and proximity)
  
• Distance traveled
• Change in compass bearing (with a threshold)

I understand that polling the GPS radio does drain the battery, as will polling the magnetometer, but I would trust apple to put in some smart limits on the update frequency to preseve battery. Developers would have to deal with a delay, and a lack of accuracy, but I'd certainly prefer that to users complaing about a dead battery because of my app. Perhaps users could set a polling frequency under the Settings for Location Services similarly to how mail server polling is configured (options like Off, 15, 30 or 60 minutes).

This for example might allow an app developer like TomTom to alert a driver about an upcoming turn, even if the application was not active. I have quite a few ideas about good ways to use this capability and would love for Apple to make this available.