When you're looking at another avatar (or yourself), the first HUD button changes to the "Fashion Syp" mode , and it will display who are you looking at.
If you click the Fashion Spy button, Shopalicious scans what the person you're looking at is wearing and will display a "style card" once it's done gathering the information.
The style card contains the name of the item and it's creator and, more interestingly, either a link to the item's Marketplace page or to the creator's Marketplace shop if the item couldn't be found.
Also, if a lookmark is available for an inworld location where you can get the item, it will give you the lookmark URL. As usual, clicking it will display the map so can teleport to the location and offer you to focus the camera on the lookmark once you arrive.