I have the Tire Minder TPMS system, small sensors screw onto the valve stems and there is a small display that you can have in the cab. Display is about the 2"x4" so not huge, and is very loud when an alarm goes off. I bought it for my 5er and used it for both the tires on the trailer and the 2004, new truck has TPMS so only using for trailers now, It has saved me once with a rapid pressure loss on my GN trailer.
EDIT [ I did swap valve stems for steel ones due to the mass of the sensor and I buddy reporting that he had stem cracking on his 5er and suspected that was the root cause, other than that extra step, they have been rock solid]