I am going to try this one out - it is free -

Mobimileage Free

Need to track the miles that you drive?

Mobimileage will automate the process for you: simply hit the "Start" button at the beginning of the trip, and "Stop" at the end, and the app will do the rest. Email yourself the CSV file from the app and keep accurate records.

Features:

• One touch to start and stop mileage tracking
• Continues to track mileage in the background or during calls
• Track miles for multiple vehicles or businesses
• Stored IRS deduction rates for Business, Medical, Moving, etc.
• International support: automatically convert logged distances to kilometers or miles
• Optional odometer input at start of each trip

Now available for free in the App Store!

http://rovingscreens.com/apps/