Stronghold has released a set of APIs that developers can use to add to apps a variety of payment instruments including Bitcoin, Ethereum, and Lumens. The APIs also allow apps to leverage Stronghold platform capabilities such as generate quotes, trade cryptocurrencies, and get available venues.
SumUp, a mobile payments rising star, recently announced an API that allows third party apps to accept credit card and cash payments without leaving the app. Prior to the API, SumUp users and customers were required to use the SumUp app in isolation from the merchant app to utilize the slick mobile payments platform.
Every day ProgrammableWeb has a Mashup of the Day featured on the home page and the Mashup Dashboard. Today's is a unique one in that there's a lot more money at stake than usual: it's the Salesforce for Google AdWords application which combines Salesforce.com and Google AdWords.