When time is of the essence, you want to get in a workout that you can count.  It may not be as easy as you think on your own.  It takes a great deal of imagination to be successful at this style of workout.  If you do not yet have any ideas on how to do quick workouts then I recommend you use the internet to assisst you in your quest.  These days you might even find someone to workout with right online.  That would be exceptionally nice if you choose to do your workouts at home instead of the gym.