I'm wondering if it's possible to use this somewhat modified IK-looking but no actual IK rig in Unity http://www.blendercookie.com/2010/05/13/rigging-easy-to-animate-fingers/
Depends what you mean by "use it in Unity". If you mean import animations made by such rig, then yes. If you mean use the IK-rig somehow in Unity, then I'm quite sure there is a lot of work to be done...