First of all, I'm not pregnant right now, so don't get the wrong idea from the fact that I'm writing this review. But when I was pregnant with my daughter not so long ago, I used a fantastic app called iPregnant to keep track of the various ups, downs, and data points. There is a free version which is limited by lack of password protection, lack of photo support, and a few other things, but once I started using it, I bought the full version, since it's only $0.99.
When you install it, it asks for your due date, which it uses for obvious calculations. Each day it lets you enter in all sorts of data, such as your mood, whether you exercised that day (or not), your weight, fetal movement, dr appointments, if you were sick, whether you had a "love connection"' and general notes. It will also store a photo if you are tracking your progress by pictures. There are also four custom checkmarks that you can configure however you wish. I set one up for "milk drank" and one for "vitamins taken" which helped me, as I'm the forgetful sort, and probably wouldn't have stayed on track with regular prenatal vitamins without the daily reminder.
It also has a daily view that tells you your due date, current trimester, how far along (in weeks and days), time left (in weeks and days), baby's likely weight, and baby's likely length. It lets you save your name ideas and gives you access to the "top 1000" names (based on US 2008 data). You can password protect the app, export the data to email, and change the units between US and metric. It also allows you to see sample 3D ultrasound pics from weeks 10 to 38 courtesy of http://www.windowtotheworld.co.uk.
This app was super handy when going on regular checkups to the doctor as I could note various symptoms each day and then be able to look back and give the doctor details as needed. If you are pregnant or planning to become pregnant, consider trying this app to track everything you need during your pregnancy. It is available in the iTunes app store, and you can learn more about the app over at http://www.winkpass.com. You could definitely go with the free version and then upgrade if you want to the paid version, as there are not THAT many differences. I just figured for $0.99, I could get rid of the ads.