This is a great app for this type of monitoring!
I have had this app since October of 2010. It has worked flawlessly for me, with no crashes at all. I like the way it looks, and I especially love the ability to perform a quick look to see where on the tracking line I am in my cycle currently. It is also especially important to me to be able to monitor my cycle in conjunction with the moon phases, since oddly, I seem to follow the moon pretty precisely. I would really love to be able to track my migraines within this app as well, since they are cycle related, but this app does exactly what it says it will do, and it does it well. And trust me, I am one picky app user.