A reader contacted me to remind me that the new RFID sensor from Codatex is also LEGO Certified - I posted a short while back about HiTechnic's sensors being certified and I should have also included the RFID sensor.
LEGO Certified Hardware means:
● 100% compatible with Mindstorms NXT
● Meet the highest LEGO quality standards
● Comply with all safety standards
● RoHs Compliant (certified lead free)