TENS
From wipipedia.org

TENS (Transcutaneous Electrical Nerve Stimulator) is considered a method of pain relief, and has a wide following for use in obstetric care particularly labour. There is a secondary market for TENS units in the BDSM community, where the units are used for erotic play involving electrical stimulation.
The electrodes could be attached to a butt plug or dildo to provide internal stimulation.
Care should be taken not to allow the current to cross the chest as it may interfere with the heart; people with heart problems or pacemakers and pregnant women should avoid using them altogether.
See also
External links
- E-Stim Systems UK A UK based manufacturer of low cost (under £100) TENS units
- http://www.electrastim.co.uk] A UK based manufacturer of low cost (under £100) TENS units
- Paradise Electro Stimulations One of the first makers of specialist BDSM TENS units
- Eman's Electro Stimulation Page
- SexTek