TinEye - Reverse Image Search to help find an image's source, duplicates or altered versions.
AliPrice - AliExpress Price Tracker app lets you track the price history of any item from many online retailers like AliExpress, Daraz, and Amazon, etc.
GImageReader - gImageReader is a simple Gtk/Qt front-end to the Tesseract OCR Engine.
idealo - Idealo is a free to use mobile application that helps you to find products, compare price and make an informed decision.
Yandex.Images - search for images on the internet, search by image
Camelcamelcamel - Easily monitor Amazon product prices and get alerts when they drop.