Are Tyrepal sensors any good?

Have you received any feedback or have knowledge of the efficacy of the Tyrepal sensors that monitor tyre pressures and, it is claimed, sound an alarm when they become soft and give advance warning of a puncture?

Asked on 4 July 2012 by MB, via email

Answered by Honest John
I've had no reader feedback at all but, looking at the photo, they seem to be made entirely of brass, which avoids the corrosion problem of multi-metal tyre valve pressure sensors.
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