GPSLib. k? (and the ? is actually an interrobang, a !? hybrid) is GPSLib. I finally got pissed off at the spam and decided to track it down, and made !!!Backtrace, which I'll be posting a link to in just a moment, once it's up on my guild's hosting. You should be able to use it to track down ANY addon's spam through a bit of detective work.
All this does is spam the default chat frame every time an addon message is sent, with the prefix being used, and run a full debug of the stack that's calling it, outputting that data to the saved variables. With that, you should be able to find ANY addon that you're using that's sending out messages.
Now, how's that for a first post on these forums? ;)
Edit: Beware, this mod does not hard-cap the data it stores in any way. You should REALLY only run this for explicit debugging purposes. The savedvariables will get extremely bloated very quickly.