The thinking behind Logitech's K380 keyboard is pretty sound. You own several different devices - say a computer, a tablet, and a smartphone - so why not just buy one keyboard to type on all of them?
The execution is pretty solid, as well. The Bluetooth keyboard has a trio of brightly colored buttons along the top row. Each can be assigned to a different device, so you can swap between the three.
There probably aren't too many scenarios in which a user will find themselves quickly switching among the three, but that's kind of beside the point. The idea is that you've got the keyboard lying around when you need it.
The design of the thing is pretty unique, as well, trading the standard square QWERTY buttons for round ones. The design decision seems to be more aesthetic than anything else, but it certainly helps the keyboard stand out from the square pack - as do the brightly colored options.
And while it doesn't roll up or fold, the keyboard is reasonably portable as well. It'll slip into a laptop bag, no problem.
Then there's the M535, a matching mouse at the same $40 price point. Would have been nice if Logitech bundled the two together - maybe that's coming down the road.
The mouse features a laser sensor, which means it'll work on just about any surface. Matching colors aside, the mouse isn't quite as visually interesting as the keyboard. It's certainly company, though, at about half the size of a standard desktop mouse.