Residex works via sales history. Unfortuantely like most property reports, the data tends to be a few months out of date at the time of publication. Residex does allow for this in its estimates, but it's not always perfect.
Myself and several other's here have subscriptions to Residex. If you email me 'peter @ sagelending . com . au' with a property address or suburb, I'll be happy to send you a report.