Notice today in the Lidl middle aisle are selling TENS pens. These are battery powered all in one units and indeed resembles a pen.

Anyone had any experience with one and know if they have perverse potential.

i have had one of those for 10 years i found in on the internet and think it cost 19.00 I still use it for on my neck and hands or any area there is some pain. I works very well.
I have heard many others use for legs and feet and even the groin area. I also like to use vibration for pain things like that. I also have some Tensor pads that give small elector
tingles that feel good when you need it. Works well for back problems or shoulders too.