Make a Stats / Deck Tracker for Eternal the Card Game.
You've got a consumer base, and a good product history.
Get to it before some other slob makes a half baked rip off.
Oleg Anashkin commented
There is one already, you can use it: https://github.com/extesy/decktracker/
I think this would be a really good idea haha.
Literally came here to post this