This impressive hack by IDEO labs makes a 67-inch rear-projection TV into a multi-touch display. They’ve mounted IR cameras into the TV and added laser projectors to the corners of the display, which are interrupted by your fingers and detected by the cameras. It’s a lot like the Surface approach, but more compact. A lot more money and testing has gone into the Surface, so it almost certainly works better, but the hardware is limited and this solution can be conceivably installed into any rear-projection TV.
Unfortunately, their claims of being the first to make an off-the-shelf TV into a multi-touch display are not quite accurate. One of our favorite finds from CES, the iTable, is far simpler to install and requires nothing but a USB port and some custom software. Total cost for a similarly sized iTable overlay is significantly more expensive, but then again you don’t have to buy the pieces at Radio Shack and mount them inside your TV’s casing. Both are certainly a lot cheaper than a Surface.
They’ve documented the process quite well, however, and it’s interesting to go through. If you’re interested in how these things are set up and how perhaps to do some of hacking of your own, this has a lot of good information in it.