Something very irritating about the app store is that you have to buy the app before you know whether its a winner or a dog. I guess the rationale is that its "only a couple a bucks"- but its like a license to dip into tens of thousands of wallets. PS: I am an architect who expected to actually use this thing once in a while. I had the impression that it somehow cleverly used the iphone camera & parallax theory to automatically & instantly calculate distances (like some auto focus cameras do). Forget about it.