It is quitting time, and you know the drill. You grab your coat and slip on your Bluetooth for a quick call with a client on the commute home. You stop at the grocery store and, while you are in line, pluck out your BlackBerry to respond to emails. You arrive home, sit down to dinner and try hard to resist the flashing red light on your smartphone. Dinner is done: Time to check your email again, clear the dishes, and sit on the couch for some TV — with your computer on your lap, of course.