API or Application Program Interface, is a set of predefined protocols, routines and tools for building some software applications. A good API makes it easier to develop a program by providing all the building blocks. Different Indian railways APIs, provided by RailPNRAPI, serves the same purpose. They are simple web based APIs for checking PNR status, getting station information by station code, checking Indian railways train route and schedule, checking seat availability and much more. The output of Indian railways APIs can be get in XML and JSON formats based on your need. For complete list of available API's and details see here 

Using the SendGrid API to send emails from your mobile apps SendGrid  is a cloud-based service that exposes and easy-to-use API to send emails from your apps, and Appcelerator apps are no exception. Sendgrid just published an Appcelerator library that makes it even easier to use. To use it, first sign up for a free SendGrid account at  http://sendgrid.com . The user name and password you choose will be the ones you’ll use for the library. The library is currently hosted on  GitHub  and soon will be available in the Appcelerator Marketplace. Locate the file  tisendgrid.js  and copy it to your project folder. For more information see here

New APIs Localytics Localytics is a marketing and analytics platform for web and mobile applications. Some features of Localytics include engagement analysis, segmentation, and acquisition management. The Localytics API allows developers to access and integrate the functionality of Localytics with other applications. Some example API methods including managing sessions, managing events, and tagging. Agregador Financiero Agregador Financiero is a financial aggregator aimed to help streamline the financial transaction collection process. The site allows users to input bank information, which is stored locally, and specify movements within a website. The service then accesses all entered banks, pulls financial transactions from each, and compiles the information into spreadsheets. The Agregador Financiero API allows users to automate the process of data collection. An account is required with service.