We use engine shutdowns on all of our forklifts. It will shut down the engine for:
1) low oil pressure (yellow wire)
2) high engine temp (blue wire)
3) optional (trans temp, low oil level, etc) It all depends on what sensor you install and wire it up to. (green wire)
Search for Clark forklift P/N 1831955 (sometimes listed as CL1831955).
It doesnt come with sensors, you have to supply them (you can tap into existing switches). It works of idiot light sensors, when they ground it will sound an alarm for 30 seconds, then shut the engine down and blows the horn (or what ever you wire the orange wire up to). You can start it back up, if the sensor is still grounded, you have another 30 seconds.
Its a very easy system to install. 6 wires total. I've installed around 50+ of them. We've had about 2-3 go bad in the past 12 years.
A company called Kysor also makes a kit, found on some bigger trucks and equipment. That one is expensive. The Clark setup can usually be found for about $150 or so.