In Arcmap, there is a tool called 'Fishnet' that takes a polygon and a number, and creates a fishnet of rectangular cells.
Is there an equivilent tool available within QML/App Studio out of the box?
ArcGIS Runtime does not have this functionality built in. You could create a GP Service, and manually call it with some network requests. Quartz will have an actual API for calling GP Services, so this will become easier in the future.
Retrieving data ...