StackSocial offers the Leap Motion Controller for Windows and Mac, model no. LM-010, bundled with a $20 Leap Motion App Store Credit for $79.99 with free shipping. Assuming you use the credit, that's the lowest total price we could find for the controller by $20, although we saw it for $8 less in December. (Most retailers are charging $80 for the controller alone now.) The Leap Motion Controller uses the space between you and your computer to track the movement of your hands at a rate of 200 frames per second. It purports to follow all 10 fingers up to 1/100th of a millimeter, making it significantly more sensitive than existing motion-control technology. Deal ends May 8.