It's a HHO generator, the American you tubers seem to get over excited about them, they have been around for a while now.
Apparently the oil industry has an elite team to kill anyone that tries to develop it/conspiracy etc etc.
The problem is the amount of electricity required for the separation of Hydrogen from it's oxygen counter part in H20 is greater than the energy released from the combustion of the hydrogen (i.e you supply more energy than you get) which is why they are calling them "boosters" rather than running 100% HHO.
If you could get the battery to supply the electricity for the separation and have a rate of Hydrogen production great enough to power the car and recharge the battery it would work, but were a while off that... especially trying to think about storing all that hydrogen.
but they are claiming that they massivly improve fuel consumption! not purely run on them just help cut fuel costs! supposedly they were big in the war when fuel was scarce but they are supposedly making a comeback now fuel is this highly priced