A Japanese Apartment complex is installing a door lock system that works via mobile phone.

It is not based on RFID like the locks we reported about recently. The door opens via a code typed into the mobile phone. The key code is apparently managed centrally by the company. So the code needs to be transmitted somehow. The article is not going into details here.
Such a system is more expensive to install, but saves money on the long run, because locks do not have to be exchanged and no keys have to be made.
More details on Nikkei.Net (Subscription).

To get rid of keys is a good idea. The mobile phone is more and more becoming the universal device. Some of the already existing mobile phone functions are: camera, music player, pda, payment and now access control.