I wonder how difficult it would be to come up with a means to determine the peak RPMs an engine has reached. This would be similar to what is offered by the aftermarket tachometer manufacturers with a peak hold option and re-set function.
The unit could be installed under the hood and out-of-sight only to be checked if necessary to determine if an over-rev condition had been experienced. It could also be used to tell the owner how another driver had treated the engine; such as when the car is in for service/repair, valet parking, or when a friend or other family member drives it.
With the electronic technology available today I would think this could even be done without the need to physically attach anything to the ignition coil, etc. Possibly only a loop type clamp or even nothing at all using proximity. It could be made to be temporarily installed and easily removed or permanately installed.
I think it would be a great thing to settle the nerves.
Would they sell like "hot cakes"?
Any thoughts from you gurus out there?