Well, I have a little experience in Pokemon overall, and as far as I know, Wurmple or Nincada don't need evolution items to evolve. The Wurmple's evolution depends on its personality value (yes, in main games Pokemon have personalities!), and when Nincada evolves into Ninjask, you might have an empty slot in your team and an extra Poke Ball. If so, you get Shedinja in addition.
But speaking about evolution items and stones, there's a big difference between them, although it's not implemented into Pokemon GO. Firstly, evolution items are given to Pokemon, and allow them to evolve while leveled up or traded. Evolution stones are less complicated - you just use them on Pokemon, no matter what level they are, and then they evolve. Even if only Sun Stone is used in later gens, there are more evolution items and stones than you can imagine. Unfortunately, not every stone (for now) is used. These stones are: Fire Stone (e.g. Vulpix into Ninetales), Water Stone (e.g. Shellder into Cloyster), Thunder Stone (e.g. Pikachu into Raichu), Leaf Stone (e.g. Gloom into Vileplume), Moon Stone (e.g. Clefairy into Clefable). But we might see them in future with releases of later gens.