https://keepa.com/ basically does that, not locally and only for Amazon tho. It has saved my wife thousands of dollars on the various things she buys. Particularly the kind of seasonal stuff. We go to alot of music festivals and the fun costumes and fuzzy stuff she loves to wear fluctuates in price like crazy throughout the year. Keepa allows her to figure out when those fluctuations generally happen. They also remind her to set a price threshold based on historical data and then forget about it until it goes back down in price.

Works great.

You could probably make that overnight. Just send a cURL to the page and look for the text of the span with the ID "priceblock_ourprice". Then log that to a comma delimited text file or something.