Ipod as game controller

[Blakduk]

I've recently seen a review of X-plane where it describes using an ipod as a virtual joystick. This inspired me to search for an app that can be used to configure an ipod to be use display slider controls for throttle, mixture, radiators, flaps etc. I've not been able to find anything that matches my idea although some come close- i've seen one for Flightsim X that uses the tilt sensor to simulate a joystick and uses sliders for rudder & throttle. This demonstrated that at least the sliders idea is achievable.
Does anyone know of an app that can be configured in the manner i described?
Or, does anyone know how to create such an app?

I have a joystick and jury-rigged rudder so i dont need them- i am just after slider controls (i'm too cheap to fork over lots of cash for throttle quadrants)