The sensor was sandwiched between the valve stem inside the tire and a nut on the outside. Very easy install; the hardest part was breaking the beads
Mine survived 3000+ miles of dirt/washboard roads, jumps, water crossings, etc...seemed bulletproof IMHO.
I've also heard good things with the SmartTire systems. The display's a little bigger and they mount using a big hose clamp, unless that's changed recently.