The newer versions of the XO have an accelerometer.  We need a chapter that describes how to write a Sugar Activity that uses it.  The article should also describe how to go about testing the Activity.  Suppose you are doing your development work on a desktop computer, which would not have an accelerometer.  Can you test your Activity there?  How would you go about it?  Can you detect the presence of an accelerometer and write your Activity so it work with or without it?