Workflow for animating object inside of object? (Organic shapes...) I'm a noob looking for best way to animate scenario below... Wrap around heart which beats.  The Wrap also inflates and deflates while heart beats.
I tried shapekeys, and although wrap is parented to heart, the keys only affect the heart...
Any suggestions?

Thanks!  Shrinkwrap looks like it might help.. I tried jacking offset to see if 
it's viable as animation key, and got these results in render... any idea what's causing the artifacting?  Face normals are all pointing outwards... (I didn't check vertex or edge norms...)
Use an armature with two bones, one for the heart and one for the wrap. Make the heart bone the parent of the wrap bone. Now when you scale the heart bone, the wrap will also scale.



You don't need to use weight painting, a simple parent object to bone will work. Parent the heart to the heart bone and the wrap to the wrap bone.



Now animate the scale of the bones -



You could also use shapekeys to give more detail during the pulsing.

Example here