The biotelemetry device (100) comprises a microcontroller (101) for generating an electrical setpoint signal (CS); a radio antenna (103) for transmitting an electromagnetic wave (EMS) by converting an incident electrical signal (IS); a radiofrequency circuit (102), interconnected between the microcontroller (101) and the radio antenna (103). The radio antenna (103) is configured such that, when the biotelemetry device (100) is placed in the biological medium (110), it can be impedance-mismatched relative to the radiofrequency circuit (102) so as to generate a reflected electrical signal (RS) by reflecting a fraction of the incident electrical signal at the same time that the radio antenna is transmitting the electromagnetic wave (EMS).