(He found it via Hack A Day, where I would eventually have seen it myself, but I've got 234 unread articles in the Hack A Day feed, so it could be a while before I get to it.)
The man has made a transformer.
The transformer's secondary winding looks like a suspension component from a large four-wheel-drive vehicle.
You could moor a ship with this stuff.
There is, I must warn you, a certain amount of profanity in the video.
I think it is entirely justified, given that in this gentleman's estimation thirty thousand amps does not qualify as "serious amps".
"I've got a screwdriver what goes round corners, now!"
The immense current capacity of the transformer causes anything shorting the outputs via small contact points to instantly lose those contact points in a most impressive explosion of sparks. But since the transformer in its present configuration tops out at only about four volts open-circuit, the hazard it (as opposed to its mains-voltage power supply) poses to its operator is only one of burning yourself on hot conductive objects, not electrocution.
"Don't touch anything electrified" is one of those general rules of thumb like "don't put metal in a microwave oven" that are easy to explain to people, but which do not actually apply in every situation.
I still wouldn't want to walk around this guy's house blindfolded, though.