What's the best iPhone app for calculating how many calories I burn every Mile I ride my bike?

I wish my bike odometer for my mountain bike could tell me how many calories I've burned

Just figure about 35 calories per mile. They do make cyclocomputers that will record calories burned. If you really want to lose weigh record how many calories you eat.

Thats not accurate anyways, to many factors from person to person.

You don't need an app. Just a knowledge of your distance ridden. We all use 35 calories per mile.

For a reasonably accurate calorie counter, you need something to monitor your heart rate. There are HRMs that interface with smart phones but I haven't tried one myself.