how do you do this? Smartphones existed as PDAs for 10-20yrs before iPhone. If I had shown someone my Sony Clie and said "if I make this work with your finger instead of a stylus, simplify the UI, and charge you $80+ a month for service would you be interested?". except for a few geeks like myself the answer would have been "no, that stuff is for geeks" for most people and yet here we are 10 years later and everyone has a smartphone.
So I don't really see how to "validate your market". I've got a few ideas I'm 99% sure would be successful given the correct marketing and PR but because they are new or at least new for a given country people tell me they don't get it, not interested. They might be right but it might also just something they need to correctly ibtroduced to.
Netflix comes up in my mind as an example. It seems obvious but if you'd asked Mom and Dad if they wanted internet movies 10 yrs ago theyd have looked at you like your crazy