Only automated valuation system that are considered accurate are the ones developed and used by large mortgage lenders/servicers internally. I used to work for corporate of one of the largest lenders in the country with millions of customers in their servicing portfolio. They have done enough deals throughout the country and have all the sales, comps, features, payment data in their system and have used the data to create a valuation system using ariticial intelligence. When times were good and there were alot of activity (meaning current data), these values were sometimes used in lieu of a physical appraisals for certain low risk refis, that's how much they believed in their system = accuracy.
I'm telling you all of this to support my view that no website that I know of that's available to the public would be robust enough to have such accurate data.