Intelligent psi devices are treated as equipment, or followers?
Anything that has the ability of self-determination cannot be equipment. It has to perceive itself as property to be property. If it chooses its own master, it is an associate.
Also, are they able to teach themselves new psionic abilites, or only to do that which they were designed?
That probably depends on the world rules.
Mike was recently in A Wizard In Spite of Himself, in which there were some people who were born psions. In that universe, if you weren't born a psi you couldn't become one; but if you were, you would somewhat naturally develop specific skills that were common to all psis and possibly pick up some extras that were rare but known. Some of the skills were gender-linked--guys could fly but could not levitate objects; girls could levitate objects even while sitting on them but could not fly unsupported. As long as they were in that world, they could not overcome those gender restrictions--but that didn't mean they couldn't learn new skills, as long as those skills were consistent with that world. Meanwhile, if Molly had come with Mike, that would have made her a verser, and at that point probably I would have said she can learn any psionic skill she believes she can learn. That would apply to your intelligent psionic device: if it believes it cannot learn a skill, then it cannot do so. It might be able to if it believes so.
--M. J. Young