When the Shake Weight came out, everybody immediately saw how jacking it could also be working out.  I'd bet most sales of the Shake Weight came from people buying gag gifts.  Now the Tug-Toner takes masturbation exercising to a new level.

 

Yes, I realize this isn't real.  All credit goes to Jimmy Kimmel Live!, and I can't remember the last timed I laughed this hard.  I'm more than willing to bet that if they actually made these, people would buy them.