I'd
adore a Google Earth overlay that showed rentals and/or homes for sale (preferably grabbed according to my own criteria) so that I can use things like drive time to important locations, school boundaries, etc. to find places I'd like to live.
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. :/