This little app lets you select up to 4 types corresponding to the attacking moves you've taught (or plan to teach) to a Pokemon. It then tells you how effective those types are at tackling every known Pokemon.
For example, if your Pokemon has one Normal attack and one Fighting attack you might cover a few Pokemon, but you would have nothing that can hit Ghost types. Add a Dark move in there and you cover that and more besides.
Currently it just gives you massive lists of Pokemon but I'll make this better looking soon!