Adress Book Integration?

Has anyone dabbled with OS X Address Book integration? It seems like a
simple enough protocol must be at work there for sharing addresses over
.Mac accounts. It would be great for clients to be able to enter their
contacts into address book and have them brought automatically into
their Ruby on Rails app, and perhaps vice versa. I’ve just started
looking into this and at the surface their doesn’t seem to be a lot of
discussion on this topic, but it seems like a fantastic tool to add to
the RoR toolbelt…

Maybe you can give me a feel for how do-able that is, where you would
start looking into it and if you’ve had any success in this area?

Cheers!

-C