I saw this advertised on the MCN website
http://www.motorcyclenews.com/products/cat...cumentID=155485
...'a small cut and paste from the above'...
The Auto-Unique 'Pressure Guard'
The Auto Unique Pressure Guard is a small, highly visible device that replaces your existing dust cap and monitors your tyre pressure.
It boasts a full certification from the German TUV agency, the highly regarded independent safety body, for its accuracy, sensitivity and effectiveness.
A small, tough plastic window contains two indicators, one red and one green. Any loss in pressure greater than 2 psi from when Pressure Guard is fitted means more of the warning red indicator appears in the clear cap.
They're strong and have two-built in safety features to prevent sudden air-loss should they be kicked or if you hit a kerb.
It's a simple and cost-effective way to keep your tyres and steering healthy. Suitable for both bike and car tyres *.
My only question is how do they deal with tyre pressure changes re: temperature changes. Otherwise a very good idea.
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I may try some. I'll update with any other info/research I find.