Client uses <script src="[url removed, login to view];youruserid>"></script> or similar to display widget.
Clients can upload one ad and choose a product category. Ads from the same category will not be displayed on their site. Also will have preference to products in similar area. Postcodes in australia determine state so 4*** will bring up all other 4**** or nationwide.
I don't have time to develop and can be seen at [removed by admin] it was a favour for a friend but have too many bigger clients to worry about.