Tracing a mobile phone number to the user's location is not legally possible unless you get permission from the users to know their location. There are social apps that you can keep track of your friends location such as Google Latitude. These type of friendly GPS apps do not require manual updates such as checking in on Facebook or Foursquare do.
Mobile phone providers such as AT&T also provide family locators for shared and multiple family line plans. You can check with your provider to see if they have a service like this. You can usually find information on the company website or even add the feature to your plan online instead of having to call customer service.
The other thing you can do is use a reverse lookup. Now this will not trace the caller's location of a mobile phone but it will give you the phone number owner name and address. Tracing a landline number would give you the location of the caller because it would be their service or home address, but with mobile phones this is different.
For one, mobile phone numbers are protected by privacy laws so although you can reverse lookup landline numbers for free, you will not be able to do this for mobile numbers. Secondly most reverse lookup sites that allow you to lookup mobile numbers all connect to the same data sources and databases.
Basically huge data collection companies collect and resell consumer information which can include your phone number. Other companies pick up this information and sort it for various reason, some of these companies are data brokers who's purpose is to give the information back to the consumers. Data brokers are then buying data in bulk then reselling. It used to be really expensive to get mobile phone number data because you'd have to contact a private investigator or background check service, but because it's becoming more widely available you can now get background checks and reverse mobile lookups for around fifteen or twenty bucks.
If you are going to pay for a reverse lookup service, just make sure it's a reputable site that provides easy refunds in case the data is not current. This can happen sometimes because some of the information can be weeks or months old.
Go to this site and enter a cell phone number, you will be able to get details about the phone number such as name, address, account history and billing information.