Custom vibrate pattern for an arbitrary app
Unfortunately you can only set Native apps (provided via Apple) which were on your iOS on the first install.

Some examples:


Incoming call (does not work for skype or other external apps)
New email (only works from the mail.app)
Text messages
Tweet
Facebook


Since iOS6 it has Twitter and Facebook built-in, and that's why there two are visible there for example.

Developers have no access to this preference and cannot build anything (yet) to support customization of vibrate patterns.