GPS driven location related widgets have all kinds of potential. The Dodgeball RSS feed basically allows this, but it's manual - meaning you have to explicitly "check in" to a location register a new destination. For years people have been talking about how cool it will be when GPS makes this process automatic.

The question I have is how GPS is going to be able to figure out what is a destination, and what is just a location on your way to a destination? It seems to me that there is always going to be some kind of explicit "checkin" action required to tell the service that you have arrived where you are going, and are not just passing through.