Maybe it would be possible to use multiple command activated items that are being held or worn appropriately (I assume that you cannot trigger someone elses items while they are wearing them just because you know the correct command word), however, using a spell trigger item like a wand requires concentration and understanding, not simply knowledge of the correct word to say.
That is what makes the bracer mentioned above useful, as it treats the wands as though they are being held directly by the character and not merely on your person. Otherwise you would need to use a move equivalent action to retrieve each or at best have one in each hand. Due to the effort and intent required to use a wand however, only one can be used at a time even if the character has one in each hand both with the same command words. That might make for a good feat however:
Dual Activation [Special]
Allows a character to use multiple spell trigger items simultaneously.
Prerequisite: Int 13+, Spell casting ability.
Benefit: Each time this feat it taken it allows for one additional spell trigger item to be used simultaneously, provided the character has the means or limbs to hold them all appropriately. This feat does not grant ability to use a spell trigger item not otherwise usable by the character.
Normal: Only one spell trigger item may be used at a time, as a standard action, reguardless of how many can be appropriately held by a character.