If you’re looking for a project for the weekend and the Knock Lock seems a little naff, why not try building your own Bluetooth Star Trek communicator ? This is definitely not a project for the faint of heart — expect to custom cut a circuit-board, drill some holes, add a serial port, a Bluetooth module, and a microcontroller. That said, when it’s all said and done you’ll be placing (and answering) calls the same way they do in the 23rd century: by speaking through a small, distorted speaker