There is now a free version of Carpool Calculator!

FREE VERSION: Does not allow: 1. you to zero-out what the riders owe the driver.
2. Drivers name cannot be changed in free version.

This is a super cool app for those of us that carpool to work on a regular basis. And now there is a try before you buy. Here is a link to the app via Android Zoom:

Carpool Calculator(Free) for Android

Carpool Calculator allows you to easily calculate how much each person in your carpool owes you by tracking your location through your phone's GPS. No matter how many people are in your carpool or how long your trip is, Carpool Calculator will help you keep track. Think of it like a taxi cab meter.