We created a rig with IK-constraints for humanoid characters for Blender that you can use easily for you characters and then export them to Unity. It is not that elaborated as Rigify but also not that complicated. We use it in our game Erwin’s timewarp for our character animation:
We wrote a tutorial in which we describe how to use the rig and attached the blend-file containing he rig as download:
See the Blender rig for Unity here.