Here's the setup I am envisioning:
Chromecast and android phone both connected to a WiFi router/hotspot (has x amount of data usage). My phone however has unlimited data usage and I would like to pull external content (soundcloud/netflix/youtube/etc) from my phones data network while letting the Chromecast pull data using the hotspot network.
I would be mirroring my display to the Chromecast so the Chromecast should only have to get very minimal amounts of data.
Is this possible? How can I do it? I've tried even hooking both the Chromecast and the phone to an isolated wireless router (no internet) and unfortunately my phone does not fall back to using data.