The Identity Provider in BizTalk Services (http://biztalk.net) is pretty darn cool. In general, it makes it easy to delegate identity and access control to a hosted service.
In a more general sense, BizTalk Services make it easier to break through the boundaries that can keep software systems from talking to one another.
This video demonstrates how you can apply the capabilites of the BizTalk Services Identity Provider to manage the movements of a robot. Keep in mind that even though the scenario shown in the video is a bit cooky, the concepts are more broadly applicable. This was a lot of fun to make, and I hope you enjoy it.