I did a quick search for this and while some people have asked for it, there's been no replies or comments back to them.
The Timing chart on all my runs (latest example: http://connect.garmin.com/activity/84351844) looks like I can't run a steady pace to save my life. I don't think those graphs accurately reflect my true running pace.
There is already a check box called "Average", but that simply draws a straight line through the entire run showing the over all average.
It would be nice if we could use the "Average" button in conjunction with a time select box (5 seconds, 10 seconds, 30 seconds, 1 minute, etc) over which the graph could smooth out the line with a running average of the selected time period.
It really shouldn't be too hard.... If you need help with the math, let me know, I have a couple of free hours that I could do this for you. ;)