After spending the past couple of days, I set up an opening activity with my 9th grade class using the QR codes.  The first code simply told them the order of things we were going to do on the iPad.  The code showed up on the notepad app.  It worked better than I expected.  The second QR code sent them to testmoz.com to take a pretest quiz on scientific notation.  I like this site as it allows me to set up the type of question and I set this quiz up as a multiple choice.  Once they finished, I can go back to the site and look at the report on the results.  It gives me the name of the student, their scores and the time it took them to take the quiz.  Below that is a grid that shows me how each student did on each question.  Both charts can be exported in CVS format so I can carefully analyze the results to help me design the unit better.
I was pleasantly surprised at how well it went.  I am going to try this method in other classes and will use this as one of my regular assessments.  This can help me monitor how well the students are learning the material so I do not have to retest.
Next step is to use the QR code on a homework assignment which I think I"ll try in a couple of weeks.  Please feel free to leave comments or suggestions on QR codes.