This app on Google Play lets you read Upanishads easily online. Upanishads are a collection of Vedic texts that contain the earliest emergence of some of the central religious concepts of Hinduism, Buddhism and Jainism. Tese are also known as Vedanta (“the end of the Vedas”). There are more than 200 Upanishads that are known. Of these the first dozen or so are the oldest and most important and are referred to as the principal or main Upanishads.
The app in two parts offer you access to almost a dozen of these Upanishads.
Grab the app The Upanishads Part 1 here, and download the Part 2 here. Each of the part costs Rs. 54.37.