How do they work? They replace the valve caps and the replacement caps have small, battery powered radio transmitters in them... They report to a receiver/compuer which is very small and attaches to your dash or visor using clips, velcro or screws, very flexable mounting
They work very well and report tire pressure either about once every five mintues or when there is a sudden change or a 10% drop in pressure. Normally the display is slient and dark, unless there is a tire with low pressure
Instalation is as easy as checking your tire pressure
Where do you get them... BernieD, a forum member, sells them