It's pretty much an app to control uTorrent on your PC. It works the same way the web access works in uTorrent, where you can connect via a pre-defined IP address and manage any torrents that are currently in your uTorrent. With Torrent-fu, you can also search for torrents on your phone and begin downloading them on your PC. You can also scan a barcode of an item, such as a movie, and it will search for a torrent for that movie.
The app is free, and can be found by searching for torrent-fu on the Market.