This Invisible PC Mouse Only Cost $20 to Make

This Invisible PC Mouse Only Cost $20 to Make: "Three students from MIT's Media Lab have created an invisible computer mouse costing only $20 to build. Instead of the typical hands-on peripheral, the 'invisible mouse' uses a line-capped infrared laser and an infrared tracking camera to interpret the user's hand movements. In turn, those movements are translated into on-screen actions such as button clicking and cursor placement."