I bought 10 of these sensors from Tirewise (www.tirewise.com
) in December, 2004, about six months ago. You buy a sensor for a specific tire pressure, and this valve cap replacement displays green if your pressure is OK and red if it has fallen by 10% or more.
Last week, before hitting the road, I checked all my tires with a pressure gauge. One of the inside duallies on the motor home was completely flat. The Tirewise cap had ruptured internally, letting all the air out while the rig was parked (in the shade). The Tirewise device still indicated green.
I pulled all ten off my tires and replaced them with regular valve caps. A few days later, I order a Pressure Pro system. It costs 10 times as much, but I don't expect it will cause my tire to go flat.
I sent an email, with pictures to Tirewise. I never heard back from them.