GPS location of a android/iphone/Windows device

We need a way to know, a caller that calls our office latitude and longitude during the time they called. Below is the URL of the site that has the code to do just that. [login to view URL] Please modify the code in the above site to fit what we need. This solution should be in C# language and open source. The solution must be able to work for iPhone, android, Windows devices (If possible). This app would connect to a sql server database and populate the table. If you have a better way to get this accomplished, please provide that solution and I may be concerned it.