http://leafsnap.com/

So I found this app for my iPad, and have noticed that it has many similar qualities to pokemon. Basically you can take pictures of plant leafs and it will identify them for you, and one goal is to fill out the number of species available. It seems to still be in the works, but they should definitely go the route to make this as much like a pokedex as possible.

I don't have an i-anything, but damn that looks awesome. That would be a ton of fun on hikes and such.