We like Matador's approach to rethinking everyday items in clever ways. Their Pocket Blanket is a great deal, for example. Their new Droplet is not on the same level, although it is undeniably - as much as it pains me to use this word on a Serious Gear Blog - cute.
They call the Droplet a wet bag, as in you put your wet stuff inside to keep your dry stuff dry. You could also flip that and put your dry stuff inside, but you get the idea. The Droplet comes in a drop-shaped silicone case that has a key ring, so you can clip it (with something smaller than normal carabiner size) to your gym bag/beach bag/backpack/purse whatever. All this is great but... the Droplet is not a dry bag, because it has just a drawstring closure that doesn't seal the opening very tight. That's good enough for a wet swim suit or towel, but for the price it seems like kind of limited functionality.
The thing is you can recycle/repurpose one of those ubiquitous plastic grocery bags to do the same thing. Or buy a real dry bag with roll top closure for about the same price. That said, if you don't mind paying a bit of a premium for the cute factor, the Droplet does what it says it will do.