Stripe - Online payment processing for internet businesses. Stripe is a suite of payment APIs that powers commerce for online businesses of all sizes. Use Stripe’s payment platform to accept and process payments online for easy-to-use commerce solutions.

Camelcamelcamel - Easily monitor Amazon product prices and get alerts when they drop.

PayPal - PayPal is the faster, safer way to pay online without sharing financial details, send and receive money or accept credit and debit cards as a seller

Price Tracker by Relbis Labs - Price Tracker is a command-line tool for monitoring the prices of productsFeaturesTracking prices and availability of products.Tracking Amazon Kindle books.Displaying products information in a terminal.Exporting data into Excel and YAML files.

Braintree - An all-in-one solution to accept, process, and split payments in your mobile app or online - from small business to large enterprise.

Pricy - Amazon price watch