I use these.
http://www.pitlock.com/ IMO there is no better system in place. I have both front and rear brakes locked with the wheels and front fork head bolt. The seat post lock didn't work on my Surly (wasn't compatable) so I bought the Surly Constrictor clamp and had the bolt that it came with machined with a safty pin in the center along with the seat bolt (both 8 mm I think). I don't think you can go too far with security bolts. Some people with take anything they can unbolt/unscrew.