With the PredictionIO Android SDK, users can integrate prediction features into web and mobile applications. The API is about machine learning services for developers and data scientists who are interested in building prediction projects. According to the main site, developers like this service because is customizable and scalable, while data scientists prefer the service because it provides an interface for analysis and evaluation of parallel models. See more of the SDK at https://github.com/PredictionIO/PredictionIO-Java-SDK
Google Cloud Vision API gives developers access to powerful image processing and analysis tools for use in any project. This tutorial on Google Cloud Platform shows followers how to use the API to detect faces in an image, and use the returned coordinates to draw a polygon around each face.