Does anyone have any experience of tracking the location of mobile phones

Here's what I want to do

A courier company I work for has 10 sub contractor drivers each with a mobile phone but no tracking device on the vehicle itself - the drivers themselves will all give consent to be tracked

I want to be able to send their mobile number to an application such as Google tracking ( if such a thing exists) and get a map reference and hopefully an image of the phone's location

Any bright ideas?