quick'n'dirty delay (fake) clothsim

I’m wondering about the best way of doing this. What I’d like is for some method of making a tail bone follow a head along X/Y (but not necessarily Z… keep that optional), but with a delay of maybe half a second. I know the game engine has a “slow parent” option, but I’m wanting this for animation. I don’t want to go into major CPU intensive methods like clothsim / softbody or anything which needs to be “baked”.

I’m attaching my own quick stab at the idea, although not good because the tail doesn’t “rest” after a movement.
Example here: ghost01.blend (487 KB)

Please look at the idea and let me know if there are better ways.