Ask HN: What are some iOS SDK for developers to build awesome apps?

I've found a few, but I was hoping there's more out there to play with. I'll be useful to know which SDKs are out there to make my life easier. Google search for iOS SDK is not very useful. Here's what I have so far:

Opentok - Video chat SDK (http://www.tokbox.com/live-video...)

Parse - Backend data storage/push notifications (https://www.parse.com/)

Twilio - Phone Calls, SMS via internet connection (http://www.twilio.com/api/client...)

Aviary - Photo Editing (http://www.aviary.com/ios)

Spotify - Music Streaming (https://developer.spotify.com/te...)

Rdio - Music Streaming (http://developer.rdio.com/docs/r...)

Dropbox - Store/share files (https://www.dropbox.com/develope...)

Box - Store/share files (http://developers.box.com/)