Google earlier used to have a program called Google Latitude that used to let you track the exact position of the mobile phone. Ofcourse, this was dependant on the mobile phone's internet connection and GPS co-ordinates. This service however, has been stopped by Google.
I know of a service that currently lets you track 'your' smartphone in case it is stolen/lost. This even helps in case you've simply forgotten where you've kept the phone. Its called Android Device Manager.
This service comes pre-installed on every Android smartphone these days. If you have it enabled on your cellphone and need to track it, follow these steps:
1. Head onto android.com/devicemanager on a PC
2. Login using the Google account that is used on the smartphone.
3. You would be able to see the smartphone listed and its location on a map.
4. You would also have the option of 'Ring' which will make your smartphone ring for 5 minutes even if its on the silent mode.
This app will also let you erase data on your smartphone remotely, if indeed the phone is stolen.
I hope this helps. Lemme know in case you need more help with it.