This new app is already being rolled out to users and the functionality is part of Google Play Services, which means it will be supported by all the devices running Android 2.2 and higher.
To check the new functionality in your device, navigate to Settings → Security, where you find the option called Device Administrators. There you can see Android Device Manager (ADM) and other similar apps that you may have installed, such as Lookout or Cerberus.
ADM lets users remotely locate, erase or ring a lost or stolen device by logging in to a web app on their Google account.
This functionality was available on Android for long through third party apps such as Cerberus. Now Google has decided to launch their own device locator app.