The other tools do accomplish essentially the same thing, but the one I was looking for seemed a bit more elegant in the way it could present the data.

Capture data and send them emails and info.

I've found some threads on zip codes to avoid, but could get more from here and City Data.

You may find that your county provides online access to homeowner data.  

@Blake Yarbrough How are you generating the data and sending out the letters?

Have you crunched through the local data to determine exactly what $25k can buy in your area?

For concrete masonry, as opposed to solid concrete walls, you could also have areas where the mortar just wasn't applied properly, and can be remedied with epoxy grouts or "tuck-pointing" new mortar into the joint to clean and seal it up.My recommendation would be to contact an Engineering Consulting Firm in your area (Google a few) and schedule a free consultation - bring lots of pictures, any historic data you have on the house, etc. 

I thought the data would be interesting for both current and future investors.

Additionally, although there's no rental data going back that far in history, I also guarantee that rents have experienced similar (or quite possibly more) exponential growth. 

Builders built the same floor plans all over the city so we have real data to support what I am about to say.