Comment Re:Passive RFID tags implanted into the balls (Score 1) 239
There have been some quite tiny absolute pressure gauges developed for cryogenic applications (they'll work fine at room temp, too). I think the company that made them dropped them from the line for lack of interest, but they can be made quite small. Hook it to an RFID chip in a way that the pressure value affects the response of the RFID, and you don't even need power-- just a quick scan with an external scanner.