Check out our Zen Wheels Micro Car at:
http://www zenwheels.com
They have servo controlled steering and a really fine throttle control for tight maneuvers with full proportional control.
You can download the free app and check it out - just go to the app store and search for ZenWheels and you should find it.
Here is a link for the app I found:
http://itunes.apple com/ca/app/zenwh...496959473?mt=8
Here is a video - more on the website, but this is YouTube:
http://youtu be/9Wd4nt_d2Ig