I forgot to mention that I also use a stop watch.  Specifically, I use a Fossil digital sports watch with a timer.  Now why on Earth do I use a timer while practicing asanas?  I use the timer to help me know when to move from one pose to another.  Currently I have it set to do infinite repetitions of 30 seconds each.  Every 30 seconds the watch beeps once and I move to the new pose.  Using this method, it takes me about 14 minutes to do one full sun salutation.  If you haven’t tried holding each pose for an extended period, you should give it a try!

Namasté