As much as we like to discuss paperlessness, the simple act of taking a pen or brush to paper or other surfaces to record visual ideas is too widely applicable to be really replaced. Working with stainless steel kitchen equipment fabricators and installers, you see ideas faxed from office to office, scrawled over, faxed back, scanned, emailed printed out, marked up again, faxed over again, and finally turned into a custom table to fit perfectly in one restaurant kitchen.

Integrating that kind of workflow will be essential for groups looking to automate construction, such as PlanGrid. Ideally, you would be able to print out a CAD drawing, draw some extra lines (or measurements) on it, scan it, and the software would somehow import the hand-drawn lines into the CAD file.

(In some ways, this situation is mirrored in sheet music - the beautiful instrumental melodies you hear are often played from sheets that have been copied, written on, erased, written again, copied after that, and written on in pen. I'm surprised nobody's developed a sheet music app.)