Since getting hit by a car on my bicycle 11 months ago and almost buying the farm, I've started exercising and running and I've dropped from upper 180s at one point to 145 currently. I'm just under 5'7" and I feel great at this weight. So don't wait for a traumatic event -- you can do it now and it's worth it. The only downside was that a year and a half ago I had finally given up, after 15 years of steady weight gain, on ever really getting back to a fit weight and I gave a closet-full of clothes away -- I had to re-buy a whole new wardrobe.
Now that I got my bragging out of the way, back to the idea thing. I can't stand stationary bikes and treadmills and stuff, so I always waited to go out and run or bike on the street -- which takes some effort to plan and is pretty easy to postpone endlessly.
An idea I had a few years ago is to combine a video game back end with an exercise machine front end/user interface so that for example you get to go faster/fly higher/avoid obstacles/whatever depending on how hard you pedal or row or whatever on the exercise machine. Biking in techno-punk traffic, racing pedal-powered airplanes through tight mountain or high-rise terrain, landing a row boat through big surf, even puzzle and first-person shooter type games where part of the control comes from your physical activity input -- the possibilities are endless...
Somebody do this! Would anybody here want to work out in a gym/video arcade setting? Can you beat the guy next to you delivering courier packages through murderous traffic? Can your team's triremes outmanoeuver and ram your opponents'? How many real or fantasy game settings can you envision for human-power controlled vehicles? Would it make sense to fly a fire-breathing dragon via a rowing-machine interface?
Giovanni