One thing that definitely comes in handy in a classroom is the ability to project or broadcast information from your device (or a student device) onto a projector screen or other display for everybody to easily see.
One of the first solutions people started adopting for this was AppleTV. And it does work pretty well… but only for Apple devices. That is a problem.
Then came Chromecast, a solution which may work best with Chromebooks, but is still fairly limited — it does not allow for full screencasting / streaming of your desktop, and instead is limited to certain applications and services.
However, there is a new(ish) standard called Miracast, which runs under a similar format as Chromecast, but allows for full-screen streaming of anything you have, on many different devices. Fortunately, Miracast support is built right into Windows 8.1, so all you need is a display with built-in Miracast support (many newer TVs and projectors have this), or a Miracast receiver box that can be plugged into your non-Miracast display device: