Years ago I read about an interesting workout routine. If I recall correctly, it was brought back from Japan by shootfighter Bart Vale.
The idea is simple. Grab an ordinary deck of playing cards, and assign each suit an exercise — e.g. hearts are push-ups, diamonds are squats, clubs are sit-ups, and spades are jumping jacks. Then, draw a card, and do that many of that exercise — e.g. 7? means seven sit-ups. Face cards might mean 10 reps, or 15, or whatever. Go through the deck as quickly as possible.
What I did not realize was that the public would pay $18.95 plus shipping and handling for a custom FitDeck with printed exercises on the cards. Evidently former Navy SEAL Phil Black reported sales of $4.7 million last year with this totally stupid online business idea.