I am an active user of GOSH.app and I can say that it is a great solution for tracking prices. Yes, you can add products from almost any online store. First, you need to register on the site. After that, simply enter the link of the product you want to track. GOSH.app will track the price and notify you when it drops or new arrivals appear. It is very convenient! I also recommend you to visit https://gosh.app/pricetracker/ where you will find more instructions. Personally, I was able to save money on several items that I liked. Also, if you have several items, you can create a list and track them all at once. It saves time and helps you not to miss interesting offers. Hope this helps!