Recently, I got as a gift a Tire Pressure monitor made by NONDA
This monitor is available on Amazon .
For a car without a spare tire, I think such a device is very useful.
The monitor transmits data over Bluetooth to iPhone app, called ZUS. There is no interference with other Bluetooth communication.
The pressure sensor is implemented as a cap on the tire stem valve. The extra weight for each cap is 9g. The pressure sensor cap operates on a battery (CR1632), which is supposed to last one year with 3 hours per day driving.
On standard stem caps sticking out a bit, I replaced stems with shorter version and it looks much better now.
The ZUS receiver is hidden under the dash, powered from AUX port.
Compared to other solutions with dedicated screens, iPhone apps works best for me, because it doesn’t clutter the console with extra gauges. My phone is perfectly positioned on my wireless charger, to view the app, without any extra devices or cables visible.
The only inconvenience of this app is that it takes about 2 minutes of calibration, before it will show actual tire pressure. It would be more useful, if you could see the status after overnight parking, before you start driving. Anyway, after you start driving it will show in approximately 2 minutes, the pressure on each tire with +/- 0.5 psi accuracy. For some reason you will never see round numbers, like 29.0psi or 29.5. Instead it will show 28.9 or 29.4…kind of marketing trickery to present device as more accurate.
It will also show the temperature on each tire. In my case, the difference on each tire is up to 4 degrees, even after being in the garage overnight. Not sure about usage of such information.
Overall, I think it is a good device for the money.
Discussion on Miata forum…