I just heard about Structure's kickstarter project today (via Brin). It's already over, unfortunately, but it's one of the neatest projects I've ever heard of. You can still preorder via their website, and I probably will. The only problem right now is that I've got an iPad 2 and my wife has an iPad 3, and only 4, Air, and Retina Mini are supported.
Nothing surprising there, but it is disappointing. I'll probably get a retina mini before too long, though, and I'll follow that order with a Structure order, if so.
Essentially, though, it's a piece of hardware that attaches to the iPad. You connect it, and trigger it, and it gives a 3D layout of what it sees, with dimensions of everything (accurate to 1%, I believe). I'm not sure what I'll actually do with it, but I'm excited about the possibilities.
Plus, they'll also be releasing an SDK for programming it. Even more possibilities.