Pushups are one tool that the Army uses to correct behavior and to improve a Soldier's decision-making process. It's something that can be done almost anywhere and any time. It's also a tool that my wife and I have used to teach and correct our kids.
Bickering in the grocery store? 5 pushups. Whining at the dentist? 5 pushups. Talking back in front of his friends? 10 pushups.
Making my sons do pushups in public is a tool that has been extremely helpful and effective. It's embarrassing, but not humiliating. It's also a great exercise and will do a lot to burn off the energy that is contributing to the behavior that spawned the need for correction. Having them loudly count the pushups as they knock them out will add to the effect.
What's really interesting is the response of other people. There are three basic responses: indifference, disbelief, and admiration. While I get a kick out of all three responses, the looks of horrified disbelief are great. Typically these people are shocked that I would administer such a barbaric tactic on my sweet little angel for such a small offense. None have had the motivation to speak to me about their disapproval, but I've enjoyed the exchange of disapproving glares.
The typical response from folks of grandparenting age is the best. Usually, they'll smile and comment on what a great idea it is and encourage us to keep it up. Every now and then, another parent will laugh and threaten their kid with similar correction.