Kingii, the smallest inflatable in the world, was invented by Tom Agapiades after a good friend of his—an experienced swimmer—died from drowning. According to Tom, he decided to do something about it when he found out that more than 372,000 people drown across the world every year.
Kingii is a lightweight wristband that is to be worn in and around water. If you ever need help to stay afloat, all you have to do is pull the lever and an inflation bag will pull you (up to 280 pounds) up to the surface. Although the wristband cannot replace a lifevest, it can give you additional buoyancy. Each time you use it, you need to replace the CO2 cartridge inside (it comes with two refill cartridges). It costs $89 on Amazon or Kingii.com.