A quick google I found one of them that works
http://www.gizmocrunch.com/mobile/5055-verizon-iphone-data-throttling-unlimited-plan
That being provided this is something I wish AT&T would of done as well. Personally I like how T-Mobile handles bandwithe abusers and that is after 5gigs of data they throttle the users pretty hard. I wish AT&T would take the abusers and say after 5 gigs kick them off 3G and force them to EDGE speeds and if it is still bad reduce them another level to GPRS speeds for the rest of the billing cycle.
Still have unlimited but the abusers are killed off and the people abusing the tethering now are no going to be an issue when streaming is killed.