Transcutaneous Electrical Nerve Stimulation (TENS), a method of stimulating nerves using electrical current applied through the skin for therapeutic purposes, has been in use since the late 1970's, as have electronic units for self-administration of TENS therapy. With the recent increase in popularity of mobile devices capable of audio playback (smart phones, portable computing devices, MP3 players etc.), most TENS users already carry consumer electronic equipment capable of providing power and control to another device via its audio port. A TENS unit designed to: (a) be coupled with an audio playback capable device, (b) make use of its power and (c) rely on it for user interaction, provides a smaller, less expensive and more convenient portable treatment solution. This approach can be extended to other electrotherapy forms utilizing similar power budgets: Microcurrent Electrical Nerve Stimulation (MENS), Percutaneous Tibial Nerve Stimulation (PTNS), Electrical Muscle Stimulation/Neuromuscular Electrical Stimulation (EMS/NMES).
