Having struggled for years with screwdrivers with embedded (almost invisible) neons, I'm really impressed with this device.
I've had neon-embedded screwdrivers over the years, but I was fed up with trying to shield them from the surrounding light while I peer carefully to see if that dim glow was alight or merely just a reflection. The crunch came when I had to fix the pond pump which had a dodgy connection (I installed it in a rush ten years ago), so I was working near water with 240V wires with a power source that I suspected was broken. As it happens, it wasn't - it was alive, indicating that the problem lay somewhere else, and that the danger was in front of me.
This device is fully insulated, so it's a lot safer to use. And it works by proximity, so that I didn't have to make direct contact with the 240V wire - when the probe gets as close as 3mm, it will light up - brightly. And it's sensitive enough that I can tell which wire is actually conducting the current. All these things are important when working with lethal voltage levels.
A great product, which arrived promptly, and the guys behind it obviously care about the product. Well done.