In the course of the 1970s, handheld electronic calculators transformed the way tens of millions of people did arithmetic. Engineers abandoned slide rules, business people gave up desktop calculating ...

On the more expensive end of the spectrum due to its conveniently wireless nature, this newer TENS machine from Boots is discreet and portable – making it perfect for subtle on-the-go use ...

A semi-decent TENS machine can cost somewhere between $70 and $200, but the team here have reduced the cost tremendously simply by separating the futzing analog/contact pad part from the signal ...