It is a prank app. There is no way anyone can track a device's location by just their number without the user of that device knowing it.
We have received a lot of mails and queries asking for app that will tell the location of a person by just providing their mobile number. We have answered many that it is not technically possible to give exact location of a device by just their mobile number. However, since the request keep pouring in, we thought of creating an app that will allow users to search based on the contact numbers and when they realize it is not their exact location, we explain in the app on why the location information of a device cannot be obtained by just their phone number.