A technique for controlling lockable devices includes a key device wirelessly transmitting a first request to a server apparatus. The server apparatus receives the first request and proceeds to identify a controllable lock whose location the server apparatus has measured to be within a physical space mapped by the server apparatus, causing the identified controllable lock to emit a human-detectable indication. In response to an action by a user, the key device wirelessly transmits a second request that directs the server apparatus to toggle a lock state of the identified controllable lock, such as to lock the controllable lock or to unlock it.