My car keys have an RFID chip in them, and my car has an RFID scanner that allows me to unlock the doors and drive the car without taking the keys out of my pocket. The transceiver in my new cell phone is strong enough that it jams the RFID communication when it’s in the same pocket as my keys. I now need to get in the habit of keeping my keys and my phone in separate pockets. :-P
Edit: to be clear on the unexpected part, not only did I not foresee this issue, I’ll wager that neither the RFID makers, nor the car designers, nor the phone designers considered this confluence, either.