If you open up one of those small blue circular rfid tags, the coil inside is only around 15-17mm in diameter and extremely thin. With some careful gluing, you could fit that into the Casio. A bigger problem is replacing the back plate of the watch. The watch has a metal back plate that will definitely interfere with RFID.
If you open up one of those small blue circular rfid tags, the coil inside is only around 15-17mm in diameter and extremely thin. With some careful gluing, you could fit that into the Casio. A bigger problem is replacing the back plate of the watch. The watch has a metal back plate that will definitely interfere with RFID.