Macro to summon one's battlepet, target it and then ...

[Adrenalin]

use the Spirit Wand toy on it?

Is this possible? Is there even a macro to target your own battle pet?

[Paladance]

/summonpet [pet name] -- if renamed, use that name
/use Spirit Wand

I can't /tar any companion, however, even outside the macro. I don't think it's possible.
Still, you'll get a hand cursor to select your target.

Note that if you have a summoned pet and it happens to be targeted, you'll waste the cooldown and dismiss that pet.