I do love to use my RaspberryPi 3 for various tasks. I use it as my test server, bittorrent client, cache proxy server, and so on. Beside all of these, my favourite daily usage is to use it as streaming device just like a chromecast. Therefor, I want to introduce 2 solutions for this unique task. One of them is an open source project which it has great android app, Chrome/Firefox extensions and also a very nice web interface. The other one is only an android app but it has further features. The best side of this two softwares are that you can use them together.
Before the start use raspberry pi for streaming I strongly suggest config your raspberry device IP address as a static ip. Than, you may want to edit your host files as well.