[khangtoh]

I'm struggling to see what is the difference between the native iOS UIActivity vs Ink.

http://developer.apple.com/library/ios/documentation/uikit/r...

I thought that's what UIActivity does and many applications are already using this particular feature to share photos between apps.

[brettcvz]

The primary difference is that Ink allows for applications to register new actions across applications, and to launch content directly into other applications as well. Think of Ink as a cross-application version of UIActivity that's open to anyone registering handlers, as opposed to only being able to use the UIActivity's of your own app or the system provided ones.