When you say "mobile grooming service" I'm assuming you mean for your pets. If that's the case, then I always recommend Pooch Spa. See my review below for more information:
I highly recommend Pooch Spa as a mobile dog grooming company. They were recommended to us by our vet, Alpine Animal Clinic in Issaquah. We've been working with them for over a year now and will never take our dog to another groomer, especially not to a "brick and mortar" store.
Pooch Spa rolls up into our driveway at the designated time, picks up our feisty Maltese at the door, and whisks him away for an hour or so of grooming in their well-equipped van. He comes back clean and beautiful, with very few signs of stress. (When we used to take him to regular groomers, he always seemed to be on edge after a day of sitting in a cage alongside 20 other dogs.)
Note also that our dog has a special need that Pooch Spa handles with grace. He cannot have the neck harness around his neck, due to a collapsing trachea. They use a tummy strap instead and somehow manage to convince our little guy to stand still for the entire time he's with them.
For more information about them, go to their website, where you can find all their contact info: