A time tracking application that tracks the amount of time a user spends on a particular project (charge number).  You should be able to create new tracker easily and for every project you are on.  They should be independent and should allow only one tracker to run at a time (unless over-ridden in a settings dialog).  Additionally, after the end of a day, the tracked progress should be saved to a file so that the user can chart their hours per task over a given length of time.