Quick inquiry. I'm not sure I get how this works. Once faithful hound is discharged and starts barking, it can attack nearby creatures, but only within 5 feet? But it has a range of close, so is the dog stationary, only able to attack in the 5 feet from where it was cast, or does it cover an area, randomly attacking anyone in range?
Relevent Juicy Bits:
Range: Close (25 ft. + 5 ft./2 levels)
You conjure up a phantom watchdog that is invisible to everyone but yourself. It then guards the area where it was conjured (it does not move). The hound immediately starts barking loudly if any Small or larger creature approaches within 30 feet of it. (Those within 30 feet of the hound when it is conjured may move about in the area, but if they leave and return, they activate the barking.) The hound sees invisible and ethereal creatures. It does not react to figments, but it does react to shadow illusions.
If an intruder approaches to within 5 feet of the hound, the dog stops barking and delivers a vicious bite (+10 attack bonus, 2d6+3 points of piercing damage) once per round. The dog also gets the bonuses appropriate to an invisible creature.
The dog is considered ready to bite intruders, so it delivers its first bite on the intruder’s turn. Its bite is the equivalent of a magic weapon for the purpose of damage reduction. The hound cannot be attacked, but it can be dispelled.
The invisible dog is effectively chained to a five-foot chain anchored wherever you placed it. It doesn't move, but if you can someone cause the flooring it was cast upon to move--for example, putting your doggy in the middle of a flying carpet--you could move it around from location to location.
Though it might be used for odd combat maneuvers, I see nothing wrong with summoning faithful Fido in the middle of your floating disk so he can better guard your levitating pile of loot as you walk it out of the dungeon.