MSD makes "Engine Knock Alert" http://www.msdignition.com/tool_8.htm
I just installed a knocklink, although I haven't seen any det yet I think it is pretty sensitive. I can see low level (green light) activity when I really get on it and I'm not even sure that I installed the sensor correctly. I used the bolt that is right next to the stock sensor. There was a bracket already on the bolt so I put the sensor on top of the bracket, using a longer bolt. I don't know if the bracket affects the sensitivity of the sensor or not.