The GReddy MMS is a nice product, but if you want simplicty which IMO is all you need, lol this product is as simple for controling & installing as you can get!
MSD Digital RPM Window Switch
Look no further – MSD's new Digital RPM Window Switch will do it all! This new Switch will accept an input rpm signal from a coil negative terminal (for stock ignitions), a tach output from an ignition control, an ECU tach output or even a 5 volt tach signal. Another great feature is that no rpm modules are needed! The rpm activation points are programmed by simply scrolling through the LED display to your desired rpm amounts. The switch has two outputs; one normally open, the other is normally closed. It can be programmed from 200 rpm to 15,000 rpm in 100 rpm increments. It can be used with an input voltage of 9 - 18 volts.
Features
Activate a circuit's On and Off point at your desired rpm.
Program the rpm and cylinder selection through the bright LED display.
Accepts an rpm signal from a 5 volt tach signal, coil negative, tach output of an ignition or through an ECU.
Ideal to control a shot of nitrous on nearly any engine combination.