If you like your bears sticky, you want GummiBears.
By default, hitting an action button that has a spell on it (say Tranquility) while in bear or cat form will cause you to shift back to caster form so that you can cast it. More than once a clumsy paw of mine hitting the wrong button has dropped me out of bear form while tanking; never a good thing.
There is a console variable (aka a CVar), autoUnshift, which can be set to 0 to change the games behavior so that the game will throw an error rather than unshift you when this happens. The only problem is that this CVar is account wide, not per character. So, for example, with that CVar changed my shaman has to first exit out of Ghost Wolf form to cast a spell which is annoying.
What this addon does is manage that CVar setting for you. Whenever you shift into bear form, the CVar is set so that spells won't cause an unshift. At all other times the setting is returned to the default behavior.