It would be awesome to have an Anker phone case with a built in battery, magnetic charging cable connection, and the option for wireless charging all in one. I would buy that immediately!
I would be alright with just a plain case for a galaxy S7. But a built in battery would be nice too
I personally am not big on the phone cases with a battery, as I think they make the phone too big. But it would be nice to have something like a phone case that you could use to charge your phone. No cables needed.
You may want to have a look at this recent thread...