Is there a way to measure tire pressure without using the valve? I'm trying to DIY a sort of a &quot;smart rack&quot; for a bike that can alarm me of problems like low tire pressure. Problem is that tire pressure is measured via the valve, which isn't a practical solution for this use case. Is there is a way to arrive at a similar pressure (doesn't have to be as accurate, but more accurate than the typical +/-20psi &quot;squeeze test&quot;) via some device that works with the tire directly instead of the valve (something that squeezes the tire and or laser/ultrasound)? This is for personal use, so I don't mind if the solution relies on hard-coded tire/bike dimensions.
If you were prepared to use  Schrader valves, you could install TPS valves used in car and truck tires. Size and possibly weight might make this idea impractical, and is most likely to work with MTB tires.  I suspect that road tires would be too small. You can get external sensors that screw onto the valve, or you would need to go tubeless to use the (probably better) internal sensors (presuming you can get a sensor that would fit a bicycle rim).
With such a system, you would simply read the display and have a very accurate pressure reading.