My solution to bike theft is not riding a bike. That's also my solution to not falling off a bike and breaking my face. But to those up for tempting fate, check out Kuat's Bottle Lock, a 5' cable of 8mm thick braided steel all neatly wrapped up inside what otherwise looks like a cyclist's water bottle.
The internally coiled Bottle Lock cable secures back into itself after entwining through and securing the bike's frame and both wheels. It is also fitted with a bottom compartment for key and accessory storage. Bottle Locks come in black, white, pink, and...uh...Marley? They include 2 keys. In case one gets stolen.