a system for controlling key access using a phone and internet - connected key box device . the key box device comprises a sim card programmed with a unique phone number associated with the key box . calling the phone number using any phone will provide access to the key box . a cloud computing software application then interfaces with operations programmed into a circuit board . a user then unlocks a key chamber by calling the number at a scheduled time . the key box device owner monitors and controls access to the box and its key chamber via the software application .