The AWS Mobile Java SDK interacts with the API to access cloud services. See folder model at https://github.com/aws/aws-sdk-java/tree/master/aws-java-sdk-mobile/src/main/java/com/amazonaws/services/mobile/model
Sometimes the API world can get a little meta. Cloudability is a startup focused solely on helping companies determine how much they're spending in the cloud. Now the company is entering public beta, which includes launching its Cloudability API. That makes the service another API for APIs.
Nexmo offers a series of cloud-based communication APIs that make it easy to integrate reliable communication services into any application. This tutorial by Tim Lytle on the Nexmo blog shows followers how to build a simple text message group chat using the Nexmo SMS API and PHP.