Late last year I had the crank position sensor fail on my '99. Shut me down cold miles from anywhere. What a pain! Now I carry crank position, cam position, and throttle position sensors in the Jeep. Are there any other sensors on the 4.0L Cherokee that will stop you dead when they fail?

 

Seems the CPS has one of two failure modes, intermittent usually when hot and "shut me down cold". Had both failure modes with my old '94 and 2k XJs.
I don't even want to think about changing a CPS stranded on the road.

MAP sensor
Not a sensor but if the IAC depending on the failure mode could also leave one dead in the water.

 

I think that about covers it.

 

You should carry an ignition coil. It is quite the single point of failure, and easy to change on the spot. (unless the 99 has coil packs, I can't recall the year it switched).