Contraction Master!

Makes it sound like you're in control of them, doesn't it? ;)

Actually, the Contraction Master is "your free contraction timing assistant" for the tech-savvy among us. With your computer at your birth (or iPhone), this is a very simple way to time contractions, if you're into that sort of thing. It's basically a stopwatch with a history, developed by a husband who wanted to spend less time writing and more time helping his wife through her labor.

http://contractionmaster.com/index.html

There's even a print option so you can save it for posterity.