http://www.washingtonpost.com/wp-dyn/content/article/2010/04/21/AR2010042104578.html

I mean, until they synchronize themselves, it's not like tracking one would do a lot of good.

I can just see it now -- you're using the app, she walks in and demands to know what you're "up to." Once she sees the application, you'll be running for the door, ducking the frisbee to your head that is now your $800 iPad

Code Red, indeed!

Especially since the scents, tastes and sights of an ovulating woman are SOOOO delicious.

The article says there are actually SEVERAL App which track these cycles and one does multiple woman.