A device in a pool table light that would project a craps table layout onto the felt when turned on. This would be coupled with inserts for the pockets so you don’t lose the dice and perhaps a higher backboard to bounce the dice off of.
Not exactly a cure for cancer, but I bet a few Sharper Image / Sky Mall regulars would buy one.
Some kind of interface between your answering machine and your VCR, so if you were out and realized you wanted to record something, you could “call” your VCR and program it. Of course I imagine this is technologically obsolete now. Can you program your Tivo over the web? I’m sure you probably can with MythTV or the like.
Also, wireless electricity!
That’s a much better idea than the floating blackjack table that I’ve seen in Sky Mall.
When all those herbal-infused beverages started coming out like 10 years ago, I thought about having a brewery that combined the health benefits of traditional medicine with the fun of getting hammered.
The first brew would have been called Gingko Beeroba: For the Nights You Want to Remember.
One morning in that drowsy state between asleep and awake, I had an idea for a TV sitcom hatch in my brain. It was fully grown, with characters and ideas and everything it needed. It will be a great program if I knew how it get it made.
It was an amazing experience. So amazing I actually dreamed of watching it on TV a few mornings later.
I have several products that I have been trying to market for quite a few years now.
I am not worried about anyone stealing them as I have an endless supply of new ideas and would hire or form a partnership with anyone who liked them.
Spray lube that works like WD-40 but lasts for over a year, I have made several prototype runs of cans of the stuff over the last 10 years and it works great. I invented it while I was restoring old cars as a way of getting grease into sealed hinges.
A bed heater that blows thermostatically controlled warm air under the covers all night long, it keeps you warm AND DRY. I have worn out my first prototype over 5 years and am thinking of making the MARK II.
Christmas light guide rails that are semi transparent and stay on your house all year. You have a thing like a split plastic tube with molded in clips for lights that slides up to 75 feet along the rail and around turns. (Put the ladder in one place and slide the lights onto the entire side of the house.)
Mac.
Another thing I did when I was in electronics school: I designed a car horn that played samples. With it was a microphone and a selector switch. You could record, for example, “Excuse me” on one selection and “Get out of the way!!” on another and “Beep beep!” on a third.
I’ve always wanted to create a useful and accurate propane tank gauge that would tell you the percentage of propane left in the tank. Luxury version would tell you how much grill time remaining (in something like “burner hours”, e.g. you have 4 burner-hours remaining, which would translate to 4 hours with only one burner lit, or 2 hours remaining with 2 burners lit, etc.)
I haven’t pursued it because I’m a theatre artist, not an engineer. Feel free to steal it anyone and make one, as long as you give me a free one to use 
PS. I know there are various gauges that currently exist, but the ones I’ve seen all suck.
Big Rubbermaid-type storage bins shaped and colored like coffins. That way you could store your Halloween stuff in 'em all year, and then have a cool prop for the holiday.
I worked for Marriott in the early 90s. I ran a hotel right off of I-95. Our occupancy was strong every night except Sunday, which was D-E-A-D!
We also had an electronic billboard we controlled on the highway.
My suggestion - on Sunday afternoon have the sign read “Name your own price tonight!”. The front desk staff would know the bottom rate and people could stop in, write their proposed price on the form, and the clerk could say yes or no, based on what they know about the bottom rate.
The rooms were empty anyway, right?
I was told people would never buy hotel rooms that way.
meh.
Yeah, there is a site that has ribbons like those and allows people to make their own custom ones. My favorite was this one.
I’d like to sell $1.00 plastic (lance armstrong type) bracelets, for goofy causes like:
-help conquer foot odor!
-Help stamp out blindness in Dogs"
-“help Conquer Scurvey”
I figure some idiot would buy them!
mine actually got made even though not to me due to lazynes it was the pasta pan that drained the pasta through the lid