Yes, the apps are great. There are some that allow you to point the phone in any direction and have the constelations, planets, and just about anything else you want, display on the screen. You can even point it out the ground and have the objects on the other side of the Earth displayed on the screen.
There are bird watcher apps that identify bird calls and tell you what type of bird made the sound.
Yes, yes, and yes.
My big collection of Audubon nature books are now relics....dust catchers. :)