[farout]

I go up and down a step - 50 times twice every hour. Unlikely stairs - you get little help from momentum and so burn more calories. Plus I raise my arms up and down at the same time. Looks silly but - it works.

easy to remember, easy to do, quick burst of energy; but don't get sweaty

Also - do wall pushups (25 at a shot) for 300 a day. As well as squat: hold for 1 min, every hour. Can do in bathroom or stairwell for privacy.