Ebay/FB Product Tracking Tool

Recently changed my phone to an Andriod and can't seem to find any good eBay item trackers on the app store. I'm talking about being notified instantly when a specific item shows up buy it now at a certain price point. I use to use BayWatch (https://apps.apple.com/app/id977021097?mt=8&ign-mpt=uo%3D4) on apple ios which did an ok job but lacked other features and UX is awful.

I'm thinking of building an application for this as I think what is currently out there can be improved with more features. There also isn't anything for Facebook marketplace, not that I can find (their own notification system doesn't work very well). My thinking is that with the continued growth of the second-hand market more and more people will be looking for bargains on eBay and FB. This would also be a great tool for people looking to flip. I don't think this is really solving a prominent problem, but with some good marketing to people wanting to make a bit of extra cash it may be of interest. I could be transparent with my own use of the tool and show how easy it is to make money.

The reason I want this is because I use the buying strategy of waiting for a seller to post an item at a completely undervalued price compared to the average selling price. I then buy instantly as these items usually sell quickly for obvious reasons.

In a dream world, I'd have an application that could scan the whole of eBay for items listed say 30% lower than the average price and alert me to this. At the moment though I am just currently building out my list of items manually that are good for this type of strategy and creating a saved search on the apps that exist. Since I started doing this I have got some unbelievable prices for items. All it requires is patience.

Monetisation would come through a subscription for premium features.

Let me know your thoughts on this and if you are someone that uses eBay, would you find this tool useful and what features would you like to see?