My concern would be more along the lines of... how would it tell the difference between your cell phone and the guy next to you in line? Would you need a new implant every time you changed phones? If multiple companies start doing this, will implants be universal, or will companies capitalize on "installation" fees by making their implants only work with their own phones?
Switching cell phone plans is already a major hassle. I don't think adding minor surgery to the list would improve things.