One system to definitely check out is the Tire SafeGuard. Not the cheapest perhaps but a very nice system and worth the $$$$.
Link: <a href="http://www.amazon.com/gp/product/B005JN17XW/ref=as_li_qf_sp_asin_tl?ie=UTF8&camp=1789&creative =9325&creativeASIN=B005JN17XW&linkCode=as2&tag=aff iliatechie-20">6 Tire RV/Truck Cap Sensor Tire Pressure Monitoring System (TPMS)</a><img src="http://www.assoc-amazon.com/e/ir?t=affiliatechie-20&l=as2&o=1&a=B005JN17XW" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" />