Here's how I approached this one. Solution file attached.
Fairly self explanatory this one, good practise for those who are unfamilar with building an Analytical App.
The only thing I don't like about them is I always find myself using the Fields from a connected tool option, would be nice to able to use unique records from a selected field or something like that!
Another down side with that option is that you must run the App as a workflow first, before you can see any options in the Apps dropdown menu, caught me out a few times.