DIY RPM switch

[BrutalBusa]

Hello, I'm Kinda new to electronics. I'm trying to make an RPM switch for my motorcycle. Any thoughts or suggestions where i could find a parts list and schematic? I'm also trying to figure out a way to turn a specific circut on with each gear change.....the GEAR POSISTION SENSOR on the bike changes the Resistance in a single wire with each gear, Is there a simple way i could make a light lite up with each gear change? I can take the sensor apart and solder a line to each posistion put it is kind of an intrusive procedure to get to the GPS. I'd like to monitor the single wire the same way the ECU does. Thanks in advance for any help.