I'm getting ready for the new iPhone to [likely] be announced in June, but before then… not a day goes by that I don't think about the current iPhone's usefulness.
Check out the Attendance application for the iPhone, which for $2.99 will make your attendance tracking much more streamlined. I still plan on having my students sign in (calling roll seems silly at their age and I teach classes of 45-50 most of the time). After each class, I can quickly update the information electronically and have it accessible on my iPhone anywhere and anytime.
Attendance also lets you email the information to yourself, making it that much easier to get the information into Excel for further number crunching. Each student can have a photo associated with their record, making learning names that much easier. The developer also regularly updates this application and is incredibly open to feedback.
Enjoy getting more efficient with the Attendance application. Let us know what other iPhone apps are helping you get more done.