Check this... It's a fascinating integration of physical and digital interfaces.

Audio programs like Reason and Logic have long used the "knob" metaphor to control levels and manipulate sounds, and it's always been unsatisfactory; most producers worked this out a long time ago and map different knobs and dials to keyboards and other midi-control devices. But this new tool, called SenseSurface seems to sit somewhere in between - you basically attach a plate to the back of your laptop screen and a seriies of magnetic knobs to your screen and use them to control virtual knobs on the display.

God knows if it's any good, but I like the idea and technical execution.

This is what the manufacturer says:

SenseSurface can be used with most laptops with a USB input. The sensing knobs have a custom designed movement sensor to determine position within a range of 180 degrees with a 10 bit digital output, linearity typically 1%. The magnetic knobs can be removed and repositioned immediately by picking them up and moving to a different part of screen. A unique sensing x/y matrix is attached to the rear of the laptop screen to detect the control’s position. The distance of the sensor from the screen can also be detected. The rotary controls are low friction and there are no screen finger prints as with normal touch surfaces. Linear sliders and switches can also be used on the lcd surface. For audio use, a logarithmic response can be programmed. The system is multitouch and scaleable , the number of controls on the screen is limited by the size of the screen. The screen can be at any angle.

Thanks to Nicholas Nova at Pasta&Vinegar