There are frequent test reports on tire pressure monitoring systems:
„"Mobile tire pressure monitoring systems allow for easy pressure checking, and thanks to variable adapters, they are sometimes compatible with car, motorcycle, and bicycle tires. A tread depth gauge is often integrated. However, systems permanently installed in the valve are considered more accurate and provide data to the vehicle's on-board computer."“
http://www.testberichte.de/reifen-und-felgen/2975/reifendruck-kontrollsysteme.html
However, it is important to distinguish between direct and indirect measuring systems. From 2012 onwards, the EU mandates direct measuring systems for new cars.
Upgrade now, it will be expensive in 2012: TireMoni