Great idea but not practical
I have a difficult time reading a book when I work out; I can read it but both my speed and comprehension suffer. I realize they must be walking more slowly than I do when working out given the number of calories/hour listed in the article but I can't imagine I'd be able to use the keyboard without making more typing errors than usual and therefore requiring even more proof-reading, etc. Sounds great but can't believe it won't impact productivity.