AMZ Alert - AMZ Alert provides a scalable Amazon solution that helps manage and scale Amazon seller obstacles.
Jungle Scout - Amazon product research made easy.
Metorik - Your online store's co-pilot (for WooCommerce)
Inventory Spy - Spy how many products remain on any Amazon Product’s offer listing page.
Datanamo - Amazon alerts and monitoring across 13 marketplaces. Datanamo tracks product listings without you having to spend countless hours on manual checks. Receive instant Email Alerts on product data changes
AMZScout - AMZScout extension will help you make a decision about picking a niche based on the actual data, not intuition.