Anyone tried this?
http://www.proquip.com.au/ProductPages/CGLOCK/CG_LOCK.html 

For road use you'd need to check with RTA and ADRs, and for track use, CAMS. A good 6-point harness would be hard to beat for track use.

I used one for 6 months and have taken it off. Fiddley, tended to slip as you took the belt on and off, so you were constantly adjusting it. Good idea, but not for me
Ian G