What We Like: 
The amazing thing about TapCast is that with one tap, the show you're watching will become more social, interactive, personlized and connected. You can even see what popular shows your friends like and perhaps discover a new favorite!
Why it's cool: 

TapCast is a social media platform that makes television more social and interactive via a second screen (tablet or smartphone). The "secret sauce" in its technology uses Rovi Cloud Services to provide TV viewers with an advanced social and interactive TV listings guide based on their "Likes" and personal interests.

API: 

http://developer.rovicorp.com/

Application URL: 

http://itunes.apple.com/us/app/tapcast/id451938063?mt=8

Platform: 
iPad
iPhone