I've used a Tire Minder system from Minder Research for many years on my previous TT. Just upgraded to a 5th wheel this year and although the TireMinder still seemed to work great on the new rig - I was seduced by TireMinder's latest model that just started shipping this week
. It's the TM-APP model. It comes in 4 or 6 sensors - the same sensors used by their previous systems - including the replaceable batteries. But it will handle many more sensors, which can be bought as add ons.
BUT - this system uses your iPhone or Android phone. There is a receiver that mounts somewhere (even in the glove box) in the TV that talks to the tire sensors and forwards that info via Bluetooth to the app on your phone. They also ship a repeater/booster to mount somewhere near the front of the TT, 5er or Toad to insure a solid signal.
They claim they have improved the battery life on the sensors although I've never had problems with them lasting a full season and you can get replacement batteries from TireMinder for just the cost of shipping OR you can buy these anyplace that sells hearing aid batteries (Walgreens/CVS/etc.).
IF your cell phone doesn't happen to be on - the receiver will still sound an alarm if anything happens to the tires.
I thought the new Cell phone app was a great approach however because:
1) I always have my phone, running WAZE as my navigation app - so it's always on and mounted in a perfect location. The TireMinder app simply runs behind Waze and opens itself if it has a problem to display. This means I don't have two devices mounted on my dash that I have to keep an eye on.
2) This system almost sets up itself - it was the EASIEST setup ever - just turn it on, the phone automatically finds box then start screwing in the sensors and the app finds them one at a time.
3) It has some great features - like you can tap the screen and "disconnect" the trailer sensors. So if you're unhitching and taking your TV out for dinner, it's just a few taps and the unit doesn't scream that it's lost signal from the sensors as you drive away. For that matter - you can setup sensors on a Motorhome from the sensors on a toad in separate zones and disconnect either zone.
I had been waiting for this unit to start shipping - I just received mine today and started playing with it - so far it seems to be amazing.
There is just one spot of bad news - TireMinder gave Camping World an exclusive (I assume for some period of time) so right now the only place you can buy these new units is from Camping World.
TireMinder Smart TPMS - Smartphone Based TPMS for RVs, MotorHomes, 5th Wheels, Motor Coaches and Trailers - Minder Research
As I actually get to use the unit on the road in a few weekends - I'll come back and post a review.