11-26-20 - Faced with some limitations of the design described here and the desire to create an aftermarket product that could be directly installed by the end user, we have developed a new design based on this technology.  This new design is a sensor-enabled valve extension that is installed to bike valves (at this point - other vehicle valves can follow later), and it can read pressure without any battery power.  

The new project required some new equipment and some fairly cool production techniques. Ever seen anyone injection mold into a FDM 3D printed mold?  Neither had we, but it worked great.  Ever seen low volume insert molding of electronics inside of plastic that was in reach of the DIYer?  Neither had we, but that worked great too!

Since the concept is completely different, we have created a new project page for it.  Check out the new project page at https://hackaday.io/project/176052-no-battery-nfc-pressure-sensor-for-bike-valves