A radiotelephone proximity detector including a first proximity unit having a receiver and a second proximity unit having a transmitter, wherein the units can be coupled together and the coupling can be detected. One of the units is associated with a radiotelephone and the other with a user. When the units are coupled, they are responsive to the detection of their uncoupling, whereupon the transmitter of the second proximity unit transmits a proximity signal to the receiver of the first unit. The first proximity unit estimates the proximity of the radiotelephone and the user on the basis of the received proximity signal. Thus the two units operate together such that, when coupled, at least one of the units enters a standby mode, and when uncoupled, at least one of the units sends a proximity signal to the other unit.