Pens with Infra Red LED the orange ones have gone (West Bridgford NG2)
The pen(s) were bought to use for the Wiimote Whiteboard Project (view-able on YouTube). Each pen has 3 alkaline cells (LR41), a switch and an Infra-Red L.E.D. By using a Wii controller, a Bluetooth dongle, a projector and some freeware, you can emulate a Smart-board (costing hundreds of pounds) for a few pounds. Alternatively, if stripped for parts, the LEDs could be used to replace faulty LEDs in remote controllers as used for TV or DVD players, for example.
This offer has been gifted to some one and is no longer available.