Roadie Tuner - Fine tune your guitar in seconds

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.

Fender Tune - Free guitar and bass tune iOS app

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

Epoch - Simple, with easy all-inclusive merchant integration. Powerful, with automated international customization. Flexible, for the most unique and sophisticated demands.

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