Surface. Of course, Surface is expensive -- like, unless you're a millionaire you're probably not buying one for personal use expensive. There are some DIY solutions out there, but designer and developer Seth Sandler has come up with the cheapest and easiest yet. Built from about $400 worth of material (some of which you probably have lying about your home / apartment / dungeon), the MTbiggie brings big-screen multitouch to the masses. Like the hacker's previous homebrew multitouch device, the MTmini, there's nothing particularly difficult to find here. All you need is a couple of chairs, a mirror, a projector, an infrared webcam (which you can easily hack together with some old film negatives and cardboard), a big sheet of paper and an equally large piece of clear acrylic. Just set it all up according to the instructions in the video below and in no time you be finger painting and playing Angry Birds on a screen that dwarfs your iPad -- and possibly your kitchen table, too.