Q.:  
Is it possible to associate a height (X) to a perimeter or length (Y) to get square feet (or meters) (X * Y) instead of just linear measurements?
 
A.: 
Extensions can be added to any Perimeter or Length objects, In this particular case, a generic area extension can be associated with the linear object to generate an area. Other extensions can also be used to get accurate results such as paint, drywall, masonry, siding etc. Many extensions can be combined on top af a single measurement object. Extensions also work on Area and Counter objects.  
 
You can configure your extensions in two ways: While creating your object, or after its creation, by clicking on the "Extension" taf in the Properties Panel (on the left hand side of the interface).
 

For more info about the extensions, take a look at our installed documentation by clicking the (?) question mark at the top right of Active Takeoff's interface.