Carve your number on my wall
Had a fantastic idea.
Whenever I want to make a program but don't know where to start, I'll have a shower and think about it. Unfortunately, once I return to the computer, I realize I'd forgotten to think about it.
However, with my new invention, you can program all you want while in the shower!
Okay, okay, so you can't actually compile and run the program, because installing something like that would introduce some safety issues. However, you can do it the old fashioned way — on paper! Well, technically, on the shower walls, which will act as this thing I've heard of called "paper". You will have this tool called a "marker" — which come in many different colours, so you can have colour-coded syntax! — and you can "write" with it, which is somewhat like typing.
Personally, I'm not the greatest at visualizing code in my mind, but actually being able to see it in front of me would be awesome. And then, when you're done, you just wash it off with plain old water from the shower!
Of course, there's the old saying "to do two things at once is to do neither". By this logic, my product would result in some faulty programming and some unclean people. But this defines most programmers in the first place, so I don't see a problem with it.
Off to the patent office now…