I'm doing the Walk At Home videos on YouTube. Leslie Sansone is the gal that created it. I also have some of her DVD's from 15 years ago. I used those to train for the one and only 5K I ever did!
It is a simple walking workout (4 different types of steps) with some arm movement to help with the core. Some are beginner workouts, others are advanced. Even the beginner workout gets the heart pumping.
This one is the one I'm doing post heart surgery:
Walk 500 Steps