While in Japan, we obviously kept an eye open for machines that dealt with payments by either mobiles or rfid tags.
(Having lockers in the London underground is almost unimaginable, but payments with the newly enhanced Oyster cards will be possible in the near future.)
These lockers at the train station in Nara are paid for with cash, but they ask you to phone up to the system so it can use your mobile number as the passkey. No hassle with assigned codes or keys that you might loose. Easy does it.