The Bike Handicapper
Now I wonder why nobody ever came up with this one...
If you have EVER been biking with a mixed group of people, you'll have noticed that it's always the same thing: the guys wait for the girls, the girls wait for the smokers, those with the coolest equipment wait for those with the... well, uncoolest equipment.
The bike handicapper solves this issue by making biking a social experience again (if it ever was). You attach the handicapper to the hub, enter the handicap of the OTHER guys, and the device will make pedalling harder for that person. If done correctly, everybody will be able to workout as much as they like, while they can still bike in a group. With a properly adjusted bike handicapper, an athlete could be even riding beside a five-year old and both would get their adequate training.