Kodi's solution worked only from video entities and from Photos (=Gallery) app. Screen Mirroring not avail.
rPlay's soulution 'used to work' but not anymore. Photos can sometimes be projected but not always.
CONCLUSION: Most of them are from 2013 - end 2014. There is no up to date solution in 2016.
A person tried to recreate the system and called it RaspberryCast. It works with anything that can be read by youtube-dl. To my understanding, it run -g to find direct url stream and open it in OMX Player, which didn't go well. It returns error in the log while stuck in 'ready' screen.
Another person made an 'emulated' chromecast called https://github.com/dz0ny/leapcast which is discontinued because google closed the source code?
So it means we have some data on previous chromecast that can be used for backward engineering reference?? Right?
I know I asked too much. I act as if this was easy. I am really sorry.