There is an ad-hoc comparison of a few of top existing services here: http://imagga.com/blog/imagga-and-6-alternative-image-recognition-services/ http://imagga

There is an ad-hoc comparison of a few of top existing services here: http://imagga.com/blog/imagga-and-6-alternative-image-recognition-services/ http://imagga.com/blog/imagga-and-6-alternative-image-recogn... and here: http://imagga.com/blog/some-more-image-recognition-tests-some-more-great-results/ http://imagga.com/blog/some-more-image-recognition-tests-som... Disclaimer: I'm CEO & CTO of Imagga.