Google Inbox

Google Inbox is a new app that released for mobile platforms. The android app was released on December, 2014. The iOS app released on this year. It will replace the Gmail app. You can get this from the playstore/apk file or from apple apps store.

It's not a app that can only read mails it's like a task manager like any.do. But Google Inbox has advanced features than apps like any.do. You can visit the below link to know more.
http://www.google.com/inbox/