The modded Samsung Galaxy S III has a small vibration sensor and when combined with Harrison's FingerSense software, the sensor can tell the difference between the three touch inputs based on vibrations and acoustics. A finger tip could let you select an object from the screen while a knuckle tap could act like a right-click on a mouse and show a sub-menu.
Harrison has started a company called Qeexo to sell the device and he says that the sensor can be added to the main circuit board of any smartphone. Harrison says he is in talks with major smartphone manufacturers now to bring this technology to the public. Harrison, though, says "the real magic is in the software, this artificial intelligence that lives in the heart of the phone".
source: Newscientist, YouTube via Gizmodo