I have a front wheel drive Chrysler. The weight up front squishes the front tires enough so they look under inflated.
Rather than get out my pressure gauge every time the tires look like they’re going flat, I got some valve stems that are really neat. They are rated for 32 psi and have green little rims that go red if the pressure drops a certain amount. You can tell at a glance if the tires are low or not. Tres cool.
Wow, do you have a link to wherever you bought them?
The hollow spars of the main rotor blades on the Sikorsky CH-53D Sea Stallion helicopter are pressurized. If a crack develops, they loose pressure. So a pressure indicator very similar to your tire valve indicator was fitted.
It had alternating black & white rings inside a cover with alternating clear & white rings. Fully pressurized all was white. Loss of pressure showed black-white-black-white. They were called BIMs - Blade Inspection Monitors.