“PRESSURE SHEET SENSOR” by the electromagnetic induction system..
It is simply constructed with the cell part vertically intersected by the coil and the metal sheet through the cushion. The electromagnetic coupling changes when the metal sheet, which reacts depending on the pressure, gets close to the cell part, and by detecting the coupling factor, the sheet displays the pressure of each cell independently

Just put optical sensor onto your iMAC. An external, user installable, optical multi-touch system comes in handy!

Xiroku’s optical touch hardware can detect multiple touches on screen. The firmware can resolve the position of touches , the size of each touch area and the usual mouse functions of click, drag, double-click and right-click.