Your project sounds interesting, I would like to help.
This is my undestanding and approach. You require an app that will periodically visit one (or maybe a few) retail store web pages to check for recent updates. Interesting updates are in a certain zone or they have some distinct style that distinguish them and/or they are detected by comparing the page content to a stored reference taken from the same page in a previous visit. When a "new release" event is detected (we could also have new discount or dropped promotion events, if they serve) a further action should be triggered, such as initiating an order or perhaps sending some notifications via email.
I would need to look at the target retailers web sites to be sure their pages are not protected or overly complex to scan. You surely are aware anytime they decide to restrucure their site the app will become broken or will need adjustment to follow up. Besides, if you need a seconds-time response, the app visit frequency may become noticeable and they can block the response or take other measured to avoid being observed.
I would propose a Python or PHP script, paired with a relational database (MySQL, PostgreSQL or SQLite) for this app. My bid assumes a straightforward page download and regular expression scanning logic, a readily available mail sending service and a control/status intranet page. I'm ready to go ahead, or to comment further thru Chat. Thank you.