So iPads, iTouch and iPhones have become a popular choice for AAC. There are many pros and many cons. There are also over 400 apps available on iTunes for AAC. Even though it is easier to get, I still suggest participating in an evaluation with a professional so that you choose the right app for you or your loved one. You don't want to spend so much money on an app and iDevice that may not be right for you.
Here is a comprehensive list of apps, descriptions and reviews. It is updated regularly This is just a starting point. I still suggest to go to someone to knows the apps or has them to trial before spending money on one.