Lookout, a mobile security firm, has rolled out a new app that helps users locate their lost Android phones, even without installing the app beforehand.

The free Android app, Plan B, can be installed over the web following the loss of an Android device. However, the user must have access to the Android Market Web site as well as to a Google account.

The user receives an email in his/her Gmail account after he/she downloads the app over the Web. The email tells the user that the app is locating the lost devise. The following email shows the location of the phone with the help of a Google Map.

The innovative app sends a text using SMS and makes use of cell towers and GPS to find the lost device, even when GPS is turned off.

However, Plan B does not work in case the device is turned off, or is devoid of SIM card or network connection.

The phone-locating app is currently available merely in the United States through a total of four network providers- T-Mobile, Verizon, AT&T and Sprint.