Google has offered 2-step verification for a while now. There are multiple ways of approving login but they all involved entering code from one thing to another manually. Google has now added the option to allow you to approve login on another device from your primary smartphone or tablet. You will have to set up one of your devices for this. It could be an Android device, in which case you don't have to do much on the device side, or an iOS device, where you will have to install the Google app. You can then select the device from the dropdown list in your Google account settings...
Source: http://www.gsmarena.com/google_adds_option_to_approve_login_verification_through_android_or_ios_device-news-18966.php
