I must admit that I do electrical toys

I initially bought a small TENS unit but found that the pads that came with it weren't very good. You can buy additional pads if you need them, though.

Also, I've heard that some of the older muscle toner things work well but I haven't tried them. They are cheap enough to pick up on eBay

I adapted a couple of hose clips/jubilee clips as electrodes and they work fine for CBT.

You need to experiment on yourself and see which settings suit, which are pleasurable...and which ones hurt like fuck!!

I'm sure somebody else will mention it...but play safely with electrical toys like that. DON'T use above the waist and DONT use it across the heart (i.e. connected to nipples)