I put an aftermarket TPMS system on my 4x4 van because it spends most of its time on dirt roads and I've ruined tires because I didn't know a tire was losing air. Type I got had the sensors that screw on the valve stems; the monitor plugged into a powerpoint inside the van. For 11 months the system was wonderful - at a glance I could see the pressure AND temperature of each tire. Then one day the system started malfunctioning and shortly thereafter quit altogether. The company that sold them (still under warranty for a month!) had disappeared so no help that way. I haven't replaced the system yet but I'm really interested in this topic to see which of these systems work well...and continue working for a few years!
