It would be cool if I could create a report from data returned by a stored procedure.
That would allow me to pre-process my data and return only what is needed.
I would need to pass in some parameters.
At the moment you can not create a report from a Stored Procedure.
You can setup a stored procedure (ActionButton / Stored Procedure) and have the results of a stored procedure returned as HTML or as a Table.
See: Action Button
NOTE: Please vote on this Feature Request if it interests you.