Magento - Tiny checkout module, calculate 10 cent extra

We deliver digital (text) goods per e-mail. We want an extension that calculates 0,10 cent extra when a customer checks to not only receive the order through e-mail but to also receive the order through a SMS text message using a checkbox. The only thing you need to do is build the basic extension which calculates 0,10 cent extra and handles 2 things: 1. During checkout we want the customer to be able to select the countrycode where he resides using a dropdown menu. To make it less work for you, we will fill in all the country codes ourself in the dropdown menu. 2. Alsof we want to know the telephone number of this customer which should be inserted in the databse together with his order number and the countrycode so we can use it after the checkout has been completed. After the order is marked as completed I want to be able to use these details in the database for my own PHP script. This means I'll do the rest, so you do not need to do anything with an SMS API or any fancy Magento admin functions. See the attached photoshopped example of what we want.