It's funny, but the "head, shoulders, knees, and toes" song is really similar to the first part of a sun salutation, and if you did a couple repeats of the song at increasing speeds, you'd probably get a pretty good workout. I know I'd be out of breath when I sang it with my Japanese students. The little kids always loved that one.
Five sun salutations (I love these)
Chair position, arms extended in front, open one arm to 180 degrees, return, do with other arm (10 each arm)
Arms at side, bring up to T, hold for 20 seconds, arms down to side
Sun salutation, hold in chaturanga (hover an inch above the floor in push up position) for 10 seconds
Repeat the four exercises three times