I have been tinkering on a little price drop alert scraper written in Python. It's run as a cron job, and every day it checks the prices of a list of urls (my clothing staples from various outdoor retailers, mostly) and sends me an email with any products that have gone on sale.

I've been running it for over a year, but now I have fixed it up and made a little landing page to see if there's interest for a stupid-simple price watch service like this (no need to install an extension or create an account):

https://www.curiositry.com/price-drop-alert/