android device as game controller with nexus 7

Use BTController app. Install on both devices, select one as controller device and the other as device to be controlled, then the first device acts as a keyboard input.

The app comes with several preset gamepad configurations, but they are customisable with the paid version. Well worth it - I've had no issues.

 

I'm a fan of using the ps3 controller to play games.

I don't know if it's compatible with your device but check out sixaxis controller

 

As fascinating as using my Android phone as a controller sounds, I have to jump on the controller wagon.

I just started using a Logitech Dual Action controller which is styled after the PS2 controller, and so far it has just been a matter of setting stuff up in menus with no other software required. Dead Trigger, Shadowgun, and even the home screen seem to respond to it.

 

Why wouldn't you just buy a PS3 controller for $15 on eBay and use Sixaxis. Seems way more efficient IMO.