It is not an idiom! It is a simple instruction to move away from our TV's, computer monitors and other similar items. Best wishes Bob

To me, it means to get away from your computer (something you do inside) and do more activities outside.

"to step away from" comes from a film and normally refers to the instruction from a man with the gun (or your boss) to "step away from your guns" or work. So you are "stepping out of your comfort zone". "Nudge" is also way of guiding people rather than giving instructions. So this sentence mixes something that is "guiding" replacing something that is "instructional" and links up to the spirit of the age.