The Chromecast is already a pretty cheap device, but what if you don't have one handy? Developer Sebastian Mauer is working on an emulator for Android called CheapCast. It would allow you to treat any Android device like a Chromecast, and it looks to be working just fine in his proof of concept video.
The video shows a phone sending video to a tablet, but it could be any device, even an Android HDMI stick. The app will work for any web-based streaming option that runs on the Chromecast. However, tab casting is currently unfeasible as it uses WebRTC. CheapCast also doesn't need root to work.
The Chromecast is interesting mainly because it makes it super-simple to get streaming video on your TV. I'm not sure if this emulator will be a better option than a $35 Chromecast, but it's nice to have the option to send video to any device. This functionality may be coming to Android natively at some point, but the developer community doesn't need to wait on Google. Mauer promises more updates soon.