Update: Sold out
Even if your car has tire pressure monitoring built in, it’s likely a binary system: Either your tires are fine, or they need air. But even a slight amount of under-inflation can shorten a tire’s lifespan, so a more precise monitoring system can pay for itself over time.
This one from Fullele includes four wireless transmitters and a receiver with a built-in solar panel, so you don’t even have to plug it into your car’s DC outlet (though you can if you need to). You’ll see a real-time PSI reading for all four tires, so you’ll know when it’s time to top them up. Use promo code AXAQK83B to get it for $62.