This product is one of the most amazing advancements in design and technology in the realm of water safety. Kingii first started on the crowdfunding website Indiegogo and has since taken off in sales.
Whereas flotation devices are usually bulky and inconvenient to water sport, Kingii is about the size of a soda can and is worn around the wrist. The inflation bag opens at the pull of the lever, which means that it only takes up the space when needed (as opposed to a permanently inflated airbag). It is also equipped with a whistle and compass.
It is powered by a CO2 cartridge and reusable with cartridge replacement. The only downside is that due to the shape/nature of the cartridge, it cannot be brought in carry-on luggages (learned that the hard way). Overall, it offers great convenience and flexibility to the wearer.