It costs 4.99 and contains info on his favorite annuals & perennials (plus photos); a list of independent garden centers in the US and Canada where you can buy the plants; and his advice for dealing with deer. Armitage actually rates all the plants on a scale of one to five, one being the plants that deer will not eat, and five being their favorites.
You can search for plants by zone, by shade or sun, and features such as plants grown for flowers or foliage. There are also links to his many videos on You Tube that show you how to plant, etc.
You can also leave a comment on the app -- or a question that he'll answer.
The app is by no means as comprehensive as his books ... so I hope that it will be updated one day (even if it would cost more) to include a lot more plants and nurseries. But he does add to it, so maybe a good investment for the future.
It's a great app for homeowners and amateur gardeners. The professionals would likely prefer to wait for another app that includes a lot more knowledge.