This is really awesome. I'm going to Bangkok on Saturday so I tweeted "@wtf bangkok", and it keeps tweeting me the top stories about bangkok as they happen (like the grenade attack earlier today).
Right now you can only track one thing at a time but we will be adding the feature to track multiple words soon. There is a hack in the mean time, just use "@wtf word1 OR word2".
Congrats on the short handle and the creative idea.
Some suggestions: 1) @wtf t=24hrs; Allow me to adjust the frequency. 2) @wtf -mashable; Allow me to add/remove sources. 3) @wtf "(facebook|twitter) down"; Allow for more advanced searches.
Only suggestion: let me track multiple topics!