The invention relates to the use of the modulation of an audio and/or visual signal by a variation in the impedance of at least one contact with the skin of at least one user, for the maintenance and/or development of the user's physical and/or mental abilities.The invention comprises the use of a device (100) for controlling the delivery of a medium, said device comprising: a first skin electrode (105) configured to generate electric waves, positioned against the skin of a first user; a second skin electrode (110) configured to capture electric waves, positioned against the skin of a second user, where the second user can be the first user; a detector (115) for detecting the value of an impedance parameter of the junction connecting the electrodes and passing through the contact with the skin of each user; and a control means (120) configured to transmit a medium-delivery command according to the value detected.