Ah ( @Lunati ), since you now have the code, you have my pet code too. I'll quickly explain you how it works: I've added a property (serverside only) to the entities (PlayerOwner), that gets set when the player uses an item with the <Activate>PermaPet (or just Pet). That property is then used by the pet entities' FollowPlayer() behavior, to instantiate a modified Chase behavior. The point is that pets (and drakes) are just simple entities, and that you can easily add behaviors to them.
And the rest is just simple heal behaviors from the fountains and playershootpacket attacks I take it?