Niki Talk - I've used quite a few communication apps before trying to find the right one for my nonverbal 4 years old. some of them were expensive and very difficult to use. one was pretty good but not easy to update or program (from my perspective). what I like about this app is that you can program it on the website so no matter what device the app is on (or how many devices it's on) your data will appear on all all of them and is not going to disappear if something happens to your device. the developer is friendly as well and is willing to fix issues if they occur.