Cruising the web one day.  I cannot believe what I found http://www.twirlgoround.com/
My parents bought one of the ages ago.  We called in the Whirley-gig.  We only had the two man version, but oh my the hours we spend on it.  It was blue and red and got rusty as the years went by, but we rode it to death.  I don't recall any of us hurling on it, but I believe one of the cousins or two did.  They don't make an adult version, yet.  Can't help thinking it would a great exercise and gotta wonder if you could use it to generate power.  It's nice to have a childhood memory my sibs havn't tainted.