ProfitGuru - ProfitGuru is the easiest way to find the most profits on Amazon.
Camelcamelcamel - Easily monitor Amazon product prices and get alerts when they drop.
Hirundin - Helping design, product and UX teams understand users and make decisions based on their needs and goals
Fetchee - Fetchee is a free price tracking wish list app that works with all online stores worldwide.
ConfirmKit - User research platform for teams and product people
Keepa - Price history charts and the option to be alerted on price drops for all Amazon sites.