For a year or more while I had young children I resorted to my old-familiar (and basic) step aerobics while watching Ellen or a guilty-pleasure reality TV show. The step cost very little and slid under a bed while not in use.
Tied to a regular show it becomes a new habit - the show and the exercise go hand in hand. Alternatively you can use ad breaks for more intense exercise.
While you could invest in an exercycle, rowing machine or cross-trainer as you home exercise option - here are 10 easy and low-cost ways to exercise in front of TV