Trakt for iOS
Works on iPhone and iPad.
I started watching this with absolutely no expectations, and was pleasantly surprised.
It's a great alternate history twist on the moon landing, and while I initially thought the novelty of core concept would wear off rather quickly, they've actually done a really good job at crafting a broad and nuanced "what if" scenario. It's a nice example of how one small difference can yield all sorts of unexpected results, and by the time I was around say... three episodes in, all the other series on the "currently watching" list had been sidelined by a need to find out what would happen next.
I'd definitely recommend giving it a try if you find the subject at all interesting.