This app brings up touch gamepad over any app and it now has basic Onlive gamepad emulation.
This sort of works but has some major problems at the moment. Mostly, it doesn't emulate analog sticks as far as i can tell and I can figure out how to map the LB and RB buttons. I sent the dev an email for more info.
I was able to play Sonic Adventure and Crazy Taxi since they just use a few buttons and can be played with the D-pad. Also any of the simpler games like Braid and Shatter should be perfectly playable.
We should keep an eye on this app, if they can add analog stick emulation this would be amazing.