A huge (multiple million policies) missing market that no one is covering here is motorcycle coverage. Almost every site caters to car insurance, but no one touches bikes.
I have multiple motorcycles. I'd like to buy insurance for them (already covered, but I wouldn't mind price shopping). Nearly all websites like this cater to finding you a better price on coverage for a newer car. I have a 30+ year old motorcycle and a 2 year old motorcycle. If there was a site that made it so I could find a cheaper (and better) insurance policy, I'd be totally up for it.
One key point here is 'better' as well- not just cheaper. If the insurer is likely to triple my premium after a claim, and another would only increase it by 10%, then I'd rather have the latter.
Kinda like Hipmunk- not just about the flight price purely, but the agony involved in flying that trip. No use on saving $5 on a ticket, only to need to spend 12 hours and 3 meals in an airport on layover, or stuck at an airport that will always leave me stranded with cancelations.
I doubt this is a 300 billion dollar business (it isn't), but I can only imagine there's enough money in this to employ a few dozen people and make real money.
Opportunity for someone for sure.