As has been discussed previously the important of low voltage is crucial in determining a potential accessory belt failure. I dont have a data system with warning capabilities for this (AIM Solo DL), but do have Accutech gauges and longacre oil and water pressure warning lights.
What's the best setup for a standalone indicator? I like the size and brightness of the longacre gauges. Should I be looking at something that indicates at <12.9v? Jim seemed to have an external light on his custom dash in another thread.