My husband just downloaded a free one. I guess it has the advantage over a stopwatch because it records the info. The one he got also has to option of emailing the recorded info to your caregiver, which may or may not be helpful.

I think this is something for partners, not for labouring women. My DH has his iphone practically glued to his hand constantly, so I'm sure he will have some fun with it.

And as for whether it is actually beneficial to time contractions. I recently heard a very positive birth story. The woman said that timing contractions was really helpful. Hers were roughly the same length and so her hsuband was able to count down for her. As in, halfway through, only 10 more seconds now. She said this was really helpful. But I guess that would not be the case for everyone.