Every once in a while, Google pops a new and interesting niche app out onto Google Play with nary a word, and a new app called Who's Down is the latest. The concept behind Who's Down is pretty simple, with the app acting as a way for friends to let each other know when they're free (or down, as the kids say) to do whatever.
Unfortunately, while you can go ahead and download the app for free, you actually need an invite to start using it. All we really have to go off of for how Who's Down works are the screenshots from Google Play that show off different aspects of the app.
Essentially, it looks like you can use a simple toggle to set yourself as available for a period of three hours. From there, you can set what you're down for, browse to see which of your friends are available, and chat to set up a meeting time.
If you want to, you can go ahead and download the app on Google Play now if you reside in the US. But until you receive an invite, it's likely you'll have to stick to a good old fashioned text message to set up your next "Netflix and chill" session.