We understand that you want to develop a windows phone application where you want to facilitate your user by tracking their journey trip time.
First of all we want to inform you that we are very much familiar with Windows Phone Application Development, we have already developed so many application of windows phone development. We have been developing a Windows phone application where we are synchronizing the exchange server folders. This is a both side synchronizing application where user can done maximum functionality which they can do in exchange server.
Now, coming to the main thing which is your requirement, we understand that this is basically a Timer Application. Please modify my understanding if i'm wrong.
I'm saying this because we are not using any GPRS tracking for the user. When user will start for the journey then they will start the timer from developed interface and in time of end the journey they will stop the timer. We will use a local database to store the result for each Trip.
Next thing is when user will tap on track button we will pull the record from the database and will import it in an Excel file and will send it to the user email ID. We will give the option to the user to set the email ID in time of App installation.
We are giving you the understanding from your brief description may your details description will help us a lot to identify the exact requirement.