I have been using Prayer Notes. I use the free version so it does have ads. I really like it though because it is easy to input prayer requests and then put them in a category. You can enter answers when they occur. For me it is easier than prayer cards etc. for when I am feeding the baby.
The only warning I would have is if you think you might switch over to the Pro version (only $1.99)the requests and info you have entered will not switch over.
What apps do you have that I should know about?