The Ravelco system seems to have a good reputation:
http://www.ravelcocanada.com/
This will not prevent the "yank it onto a flat bed and gone in less than 2 minutes" trick. The Ravelco device is very similar to the "ProLock" of some years ago. These were known to fail and leave the owner stranded in the middle of a parking lot. What it does, is scramble the important wiring under your dash so that only the "key" can unscramble it. For the expense and added hassle of this device, a smart and handy car owner can simply install one or two hidden "kill switches" that tap into the ignition wire, starter wire or fuel pump wire (of a modern day car). There is no ultimate theft prevention system short of an armed guard watching it the whole time you're not there. And even if you are there, ever hear of "car jackings"?
The best you can hope for is to use some care and attention on how and where you park it. Visible deterrents are always a good idea against the punks and small time car thieves. If a pro wants your car, it's gone. Have insurance.
Hang a few car thieves like they did with horse thieves and maybe the rate of theft will go down. But no, we're a nation of bleeding hearts. Death sentence is too cruel. Instead, we keep them in jail for a year or so at a cost of $100,000.00/year. (Oops, getting side tracked here.)