More than just a calculator app.
Calculog is a simple calculator with an extra feature: It logs the history in the background and lets you send it to your email address anytime. You can also edit the history to add text notes before sending. It is a simple app, but is thought to become the default calculator for every user.
Great for adding up receipts, keeping track of travel expenses or mileage. All right on your iPad.
This is a great free utility.