I think this is the problem that the "Lean Startup" methodologies aim to solve, enabling you to cheaply and quickly test out ideas in order to find the one that will satisfy the criteria you listed.
Yeah, it's such a simple thing that nerds don't seem to get. Put out ads on craigslist, adwords, indiegogo. Whatever sells, do that. The biggest problem is having more ideas than time to write them into an ad, there's too many potential products. You can outsource the creation of whatever sells so executing isn't even that big a hurdle (though you do have to be careful with initial pricing on the ad so that costs don't get you).
Do you have examples of these ads? I'd love to see how other people phrase them as I'm investigating this kind of stuff for myself at the moment.