Don't track user patterns unless it's completely anonymously. It would be unforgivable If you were to get hacked and it turns out that despite your best intentions, there is some way for a third party to reverse engineer IP addresses, usernames, hashes, Chromecast IDs, et cetera to identify your individual customers,

I concur. Was hooked after one episode.

I use product to stream audio only mp3 files to my Chromecast at night. It would be great to have an option to go to black screen so that the TV isn't lighting up the room, without having to dig out the TV specific Remote Controller to dim or turn off the screen.

auto-select the Chromecast device when a single device is detected, and then persistence once a Chromecast device is selected until and unless a second or multiple device are detected.

As well, for homes with multiple Chromecast devices present, a countdown timer to allow users to change the playback device selection from a persistent 'last device used', followed by auto-selection of the last device used from that browser if no change in device is selected, would likely be applicable the vast majority of the time.