Is there any way to set this up on the Shield so that I can cast to it without being on the same Wi-Fi?
Is there any way to set this up on the Shield so that I can cast to it without being on the same Wi-Fi?
I don't think you can do it on the Shield, but possibly your router if it supports this. Google WiFi pucks support this. You can create a guest network and designate what devices a client can access on the guest network with those devices existing on your "main private" network.
I don't believe it is possible to cast outside of your wifi with AndroidTV.
It'd either be in the Shield's settings or accessible in the Google Home mobile app.
It's only available on Chromecast devices, not Android TV with built in Cast, I'm afraid.