Android: Opera rolled out its Opera Max data management tool earlier this year, but used a waitlist model to restrict sign-ups. Now the browser is generally available to Australian and New Zealand Android users.
Max compresses data such as images and video before you download them, as well as letting you specify which apps or services can use Wi-Fi. Opera has also updated the tool to work with Android Lollipop. If you're on a tight data allowance (or just near the end of the month), it can be a useful tool to have. It runs on Android 4.0 and above.