As mentioned, what if the animal companion has this item?:
Ring of Eloquence
Source Advanced Class Guide pg. 217
Aura faint divination CL 3rd
Slot ring; Price 3,500 gp; Weight —
Fine etchings spell out the alphabets of four languages around the inside of this finely crafted silver band. The wearer gains the ability to speak and understand the four languages whose alphabets are inscribed on the ring. Normally the languages are Common, Dwarven, Elven, and Gnome. Less often, such rings are attuned to Giant, Goblin, Orc, and Undercommon, and rings with different sets of languages might also exist. The wearer retains the ability to speak in these languages even if she assumes a form normally unable to do so (such as a druid wild shaped into a wolf).
The ring also makes it easier for the wearer to find the correct words to express herself, granting a +2 competence bonus on Bluff, Diplomacy, Intimidate, and Perform (oratory) checks. Also, if the wearer is deafened and attempts to cast a spell with a verbal component, the chance of spell failure is reduced to 10%.
And therefore can speak a language. Would the animal companion then be able to activate other magical items that requires activation?
Asking this for a homebrew game I'm gming. While this means I can easily house rule on this matter, I would like to know how this would normally work.