Chromecast adoption is growing and as is appropriate Google is providing comprehensive Developer guides for select platforms:

While Chrome Apps are supported within all the major browser and therefore by extension all major OS’s I think the  lack of Windows 8 and Windows Phone 8 support is the latest in a clear pattern of aggression towards Microsoft products.

In contrast to what looks like a promising API from Google, Miracast (developed by the Wi-Fi Alliance based on interoperable standards) has no easy access API for any mobile vendor. It is kind of disappointing that the best work in this area is being developed and innovated using proprietary standards, pushed onto customers of competing and incompatible tech giants (Apple and Google).