I am interested in the convenience of diapers, but not the mess. The thought of not having to leave my seat to empty my bladder warms my heart. The problem is I would not be able to sit in the resulting mess. A friend suggested a powerful vacuum conveniently placed. When questioned about the storage he said it would blast the offending matter out with high pressure. It is an intriguing idea. Think about what it would do for crime, bad driving and crooked politicians. Those assholes will think twice about cutting you off if there is the possiblity of getting blasted by a high-powered projectile dookie. Plus, it will make every monkey envious. The problems are abuse of the system etc. Vacuums are not quite at a size where it would be practical, yet.
If practicality is the only issue, I suggest using teleportation. Once the technology is mastered it would be quite convenient. Imagine, no don't, a small piece of machinery that automatically transmits any unpleasant bit of business to the septic tank. This would also be an excellent method of birth control, provided the equipment is not bulky or awkward. Although that in itself would be a pretty good method of birth control.
Such technology as listed above would have drastic results on the population. It would be strange, I imagine, to get used to defecating or urinating in public. I am sure there would still be times when it would be a social faux pas, like when giving a gubernatorial address, but the convenience and cleanliness would be revolutionary. Gone would be the days of the greasy gas station bathroom. No more embarassing moments of holding shut the stall door because the lock is broken off. Toilet paper would become a thing of the past. It would save billions of trees.
With great ideas like these, its a wonder I'm not a millionaire.