This sounds like an interesting idea for personal projects. My boss might raise an eyebrow if he saw me playing games or surfing the web for half of my day.
I think you specifically don't want to play games or surf the internet. I work in a big building, so about once an hour I get up and go for a 5 minute stroll and come back to my desk. Though I do a lot of work with other people in the building so I guess people just think I'm going to talk to someone I'm working with.
