Yo is a notifications app where all it does is send the word "Yo" to your friends. That's it. Just "Yo." Of course, silly single-purpose apps like these are a dime a dozen -- remember those fart apps of old? -- but the thing that sets Yo apart is that it's actually attracted a whole lot of attention. More than a million dollars' worth, in fact. Yep, this seemingly frivolous app has recently raised around $1.5 million in funding, giving it a valuation close to $10 million. It's also apparently been downloaded more than 2 million times since its tongue-in-cheek April Fools' Day debut.

Crazy? Well, yes, perhaps. But it's not entirely unusual. In case you need a refresher (and probably a laugh or two), here's a look at some of the more overhyped apps in the past few years. Have any other ideas? Leave a comment and let us know of any apps we've missed.

Gallery | 10 Photos

Yo and 9 other overhyped apps