Yes you've read that right. You can play Shadowgun (and probably other games that supports game controllers) on the ASUS EEE Pad Transformer (also should work on other tablets with USB support) just by using your Android phone. Take a look at the video below:
The Droidmote server needs to be installed on the ASUS EEE Pad Transformer and the app itself costs $2.00 for the server while the Droidmote client is FREE and should be installed on your Android Phone. Take note that the server requires root to function so you have to root your tablet / transformer for this to work.
Check out the source below for the full information and coverage on turning your Android Phone to a gamepad controller without spending money on a separate device.