DatingAnyone helps you track the dating status of people on your MySpace friends list, and presumably catch them on the rebound. When there's a change in your friend's status, you're sent an email alert. The service doesn't log in as you - it simply sends out a bot to grab the status info from the profile pages.
Surprisingly, DatingAnyone isn't the only player in this space - a more lightweight service called SingleStat.us does exactly the same thing. However, SingleStat.us charges a one-time fee of $3.95 for notifications, while DatingAnyone is free. On a similar note, newly-launched Stalkerati lets you search for a person's name across multiple services - social networks, blogs and image search.
This isn't feeding the MySpace beast - it's more like leeching off it. But these services all add value, so hopefully MySpace won't feel the need to throttle them or (worse still) build an in-house version.