Originally posted by @Major Robertson:
I don't think Zillow provides aggregated data via API such as sold listings from a certain area.
Have you looked up the costs of implementing the several apis you'd be needing?
Just be careful that with everything you're adding it doesn't get too cluttered. It's usually better to add one awesome feature rather than several decent ones.
However sounds like an awesome app. Some of the features you mentioned like photo/GPS upload would be pretty cool.
I'd advise you to look up the competition and see how you can improve on what they're already doing. And always develop based on user feedback, which it seems like you plan on doing based on this post.
If you don't mind me asking where do you work? I'm a consultant doing development at Humana.
They do provide API for that. I haven't done all that much research in what other features their API offers, but sold listings is one of them. I am considering using only one RE platform at a time, but it depends on whether some of the platforms can compensate one another. I work out of Cleveland, Ohio.