There we are, the first alpha version of SIMPLE!
If you still ignore it, SIMPLE is the presence ability for SIP so it is in charge to show the current status of your SIP contacts.
This release is an alpha : this means probably a lot of bugs (but nothing destructive for the project) and not every functionalities.
So with this release, you'll be able to see the status of you sip contacts (only online, offline and away for the moment) and only for 10 minutes at least (no, don't worry, SC isn't a shareware it's just a missing functionality in the implementation).
If you use SIP, don't hesitate to use (and abuse) of SIMPLE with SC and to report in this mailing list every problem you encounter.
For the moment only one problem is being fixed, it concerns the iptel.org server (and probably every SER servers) and it will force you to reenter your password many times... Don't worry I'm on it and it will be fixed soon!