How many times have you seen something in an image and wondered who made it and where you could buy it? This problem without pigeon-holing a particular sex is one I've seen my partner go through countless times. She sees a dress, a bag or piece of jewellery, but sometimes can come up empty handed even resorting to a Google search by image search.
A desktop and companion set of apps for iOS and Android that allows people to upload both images and tag existing ones. Think of it as a site like Stack Overflow or Quora but for object tagging. Or better yet, think of it as a Shazzam or Soundhound for identifying objects in images albeit just manually.
I see user "john23" has uploaded an image asking if anyone knows where he can buy the mens leather brown bag seen in the image and who makes it. I know the brand or own the bag myself, so I tag the object with some details and a link.
This idea would ideally have a gamification aspect to it. People need an incentive to tag objects in images. Giving users points is one aspect and through affiliate revenue and advertising on the site those points can be cashed in for incentives like gift cards/prizes/cash.
Another aspect would also be the third-party sites themselves incorporating a Javascript file that would allow for image tags to show up and link within a page without breaking the third-party site.
Imagine being able to tag objects in images on Twitter, your favourite gossip website and get credits which equate to real rewards? All the while, increasing the database of tagged objects. You could even extend this out to work with other mediums including video (think Youtube or Vimeo) and sound (tag samples in an audio file on Soundcloud).
And for the next big thing: imagine being able to tag objects in movies and TV series? Bouncing off of the video idea, if you could tag objects in a movie or TV series (even tag objects modelled off of costumes and sets in a movie/TV series). This would be huge.
There are definitely existing solutions out there. One that comes to mind is called Crowdsend. Another major player is Thinglink