I'm still stoked that Blizzard's honored my work on this site with an in-game NPC. My counterpart (screenshot) is a vendor of <Pet Supplies> in WotLK, situated in the capital city of Dalaran. As of today, her goods include rope pet leashes and fetch balls. Dalaran is currently very much unfinished, so perhaps they'll be adding more to her shop as they get closer to release.
As far as these two items go, the [Rope Pet Leash] (seen with Murky in the screenshot linked above) is a reusable cosmetic item that provides a tether from you to your pet. I'm hoping a macro can be written to summon a leashed pet with a single click. I'm also curious to see how this leash affects already tethered pets, like the Dragon Kite. I'll post about that soon. We may also see other types of leashes, such as chain and leather.
The [Fetch Ball] is purchased in lots of 5 and stacks up to 10. It's a consumable that can be thrown from your inventory and retrieved by whatever pet you currently have summoned. But surprisingly, the ball doesn't wind up back in your inventory—it simply vanishes from the pet's mouth into oblivion. I'm thinking they made it a consumable as money sink. But personally, I would prefer a much more expensive ball if it would just reappear in my inventory when returned by my pet. Perhaps they'll add something like that in the future.