This is a website that matches buyers with sellers. In ordinary business, buyers go to a shop/website, find something to buy, and then purchase the item. This website will reverse the process a bit. It will allow sellers to list their items for sale (like Gumtree or eBay), but the unique part is that it will encourage buyers to list what they want. For example, I can list that I want a pair of Bluetooth wireless headphones and I'm willing to pay $50 for it. The website will try to find any existing listings - if they exist, it shows them to me. If not, it creates an alert to notify me when one is found. When a seller lists an item that matches what I want (eg the headphones at $50), the website tells the seller that a buyer has asked for this item, and it alerts the buyer that a suitable item is found. The buyer then confirms that they want it and then pay for it.
The main part is the matching algorithm. It would need to find exact matches and close matches. This means the buyers should list the items they want with as many details as possible.
This idea is intended to change the way we buy online - instead of spending time searching for what we want, we simply list what we want and then continue with the rest of our day, and then the website algorithm will do the finding and matching, and alert the buyer when something suitable has been found.