Forget the expense. They are all expensive BUT when I'm driving down the road mine scans all the tires continuously.
Tire pressure as well as temperature. I feel better when I'm on a long trip and know ahead if I have a leak.
I feel much better know what is happening and it has programmable high and low air pressure as well as high temp.
I have Truck System Tech Tire Monitor RV510 with the screw on sensors.
Usually they give you 2 year warranty and if one fails or acts erratic they will replace for free. I have my system since April 2012 and have 23,000 miles under my belt. They are worth the money.
Now all you have to do is select which manufacturer you want to get it from.
I think their are two major distributers and they all made in China.
Mine cost me $299 for a 6 sensor system with 2 year warranty.
Here is the website
Home - Truck System Technologies, Inc
I have attached the manual so you and read it first.
Here is a great YouTube Video