I used Babyroo on my iPhone. I kept track of feedings (couldn't remember when I fed for the longest time!), wet and dirty diapers, growth, bottles, when I pumped, baths, pediatrician appointments and medicines. It was very helpful when we would go in for check ups to know how many dirty diapers she had in the last 24 hours. It was very user friendly.
Similac Strong Moms app is a great. It can track breast feeding (timer for how long, reminder of which side to start on) bottle feeds (time, oz etc) diaper changes, pumping and sleeping. It's very easy to use and you can view all activity for the day on one screen and it also tracks trends.
iBabyLog here. H and I both have it on our phones so we're always in the same page about when she ate, how much, etc. We're also using it to track pumping and diapers. It's free and I would highly recommend it.
I've been using the Similac Baby Journal app. It's great for tracking feedings, diaper changes, naps and growth. I think it's great and definitely beats writing down how much LO eats and her diaper changes.
Re: What apps for tracking feeding, etc.?
Eta: it has other categories than just feeding and diapers, we use it to track all the kids' weight, height, temps, meds, etc.