App that lets you identify trees from pictures of their leaves

Thankfully the wonderful folks at Leafsnap plan on having an Android version out soon, or I'd have to rethink getting an iPad 2. Now if they could come up with an app to do the same thing for wildflowers, I'd have a couple months of fun going back through all my "And here's an example of a... yellow flower I saw a lot of that day" pictures :-)