Pokécharms

Depends on the power level of the transformation in question, I say. What did you have in mind?

Something along the lines of a tech and Pokemon mixture. A Pokémon holds an item specific to them (Like in Mega Evolution) and there form changes, to a tech version. Like the, using gadgets and such. So a simple change. They gain a typing, Mech, which is only supereffective to Mech and is neutral against everything else, and it is added like a third type.