The mapping that existing real estate and rental listing sites use are frustrating to me because searching by location is clunky -- by city or zip code or even distance as the bird flies is too vague. I want to make sure I don't spend my life commuting, that going to our dojo isn't a prohibitively long trip, that I like the school my child would be in, and that there's a nearby grocery store or grocery delivery that suits my dietary restrictions.
I want to be able to overlay whatever data is important to me -- elementary school boundaries, grocery stores or delivery areas, traffic patterns, etc -- on my home search.
I want to be able to pick a few locations and specify maximum drive times for each, then find places in the overlap (bonus points if I can input my schedule so typical traffic patterns are considered).
I have no idea how you'd make money off of it, though. :/