The Wishlist extension is made to be used alongside the WIshlist app (located at w1shlist.herokuapp.com). This extension simply highlights images on a current page, allowing the user to select one to add to their wishlist, which is displayed on the web app. Please note that you must be logged in to Wishlist to use extension.
Once you get the hang of it, it is a really nice resource!
It could be easier though if there was a direct link to the user’s wishlist in the drop down menu