The new iOS 5 integration with Twitter is great and the ability to geo-tag posts is fine and dandy. But there is a problem, when I get home and tweet I don't want to send the location, nor do I want to send the location when I pick the kids up from school or do any number of stalker/burglar friendly things. These elements are almost always related to specific physical locations that I don't want to be recorded.
So here is my next idea, the concept of physical privacy or functional bubbles, places where you draw a circle in Google Maps (or similar) and state that when you are within that bubble you do no want your location to be recorded. This could be extended to other functions on a smart phone, for instance by setting "no call" zones in places where you go fishing or setting a inverse zone for a kids smart phone so they can only access the internet when at home or school.
The concept here is that people can manage their privacy, particularly their geo-social privacy, my marking out places on a map where these features will become disabled on their smartphone. So rather than having to remember "oh I'm at home, must turn location off in Twitter" you instead just mark these zones and the features are automatically disabled on the phone as you enter into that zone. This gives parents the ability to better control what their children are accessing and gives individuals greater automatic control over the information they are sharing online.
Now the reason why I haven't just written an app to do this is I quickly realised that this needed some pretty low-level integration with the device in order to make it happen (iOS doesn't like apps changing fundamental settings!) so its something that Google or Apple would have to do rather than it being a download from an app store (unless someone proves me wrong) but I also wanted to make sure that there was published prior art in case someone in future tries to patent what is, for me, a ruddy obvious next development.