So i wanted to share what has worked for me, to have a TPMS on a budget. I know how valuable these are but couldn't afford the few hundred dollars for the ones that are highly recommend on this site just yet. My set up is a Grey wolf 26 DJSE towed with a Dodge Durango R/T.
I found one that was really meant for cars on Amazon for $50 (at the time). *some reviews said it worked for folks with trailers, so it sounded like it had decent range regardless.
https://www.amazon.com/Fullele-Wirel...ct_top?ie=UTF8
The distance the unit would work reliably according to the description was around 8M, which from my rear tires was right around the middle of my vehicle. What was important for me was select-able PSI and temp alarms and a good audible warning - i set the unit up and use the 12v outlet in the back of my Durango, which is right inside the rear door in the cargo area. Most SUVs have one back there. While i can't see the numbers going down the road, i don't need to. I just need to hear the alarm if the psi drops or the temp soars, and I can hear it all the way from the back. I have used it on a few trips and do note the readings when stopping for gas or breaks and it definitely has been working. It also has a warning when it can't read a sensor, and I have never heard it when in motion with my setup.
Hope this helps someone in my situation.