Its no practical solution, You can do 30Kmph and still be over speeding, Just picture someone doing 30Kmph in front of a school gate 5 minutes after the last bell has rung in the evening. Law enforcement with reasonable( Read Hefty) fines is the only way to change matters for good. And yes speed limiters and governors are a puzzle waiting to be cracked or by-passed.
BTW now in Chennai they are having speed governor cameras kept at highways and some places inside city. It's kept in the Chennai bye-pass highway which i use almost daily. This has helped to keep the speeds in limit for a particular flat straight stretch where people speed.
But even now people start to speed up again once we cross the speed governor(including me)!
IMO, speed limit is not the solution for the accidents though there are few people who drives recklessly. Govt. is not thinking about improvement in road conditions, better traffic management viz. plying of trucks in day time inside a city or controlling of unruly autos etc. Neither Govt. is thinking of speed limit marked lanes in the highways nor able to stop the unauthorized cuts. So manufacturing of speed limit controlled vehicles will not be effective.