RulerPhone is a fascinating concept. The premise is that you set a credit card sized object next to anything that you would like to measure and the application allows you to find semi-precise measurements by comparing sizes.
To start, you can use images saved on your iPhone or just take a picture right then and there. Simply place a credit-card sized object up against the object and snap a photograph. The objective is to then adjust the the scales for the card first, then the measured object.
The application will then show you the estimation. The estimation can be shown in foot-inches, or just inches, Metric or English measuring system, and more options.
The Good: Quite innovative, great interface
The Bad: very little real-life application.
Bottom Line: It’s a pretty handy application, but I’m not so sure how applicable I find it in everyday life. People that will need this application usually have these things called Tape-measures. I’d invest.