I have a Garmin 305 unit - it's more than a bike computer, but my husband programmed it to not count speeds below 3 or 4 mph into the average.
Ditto. I have mine set to pause below 3mph...mostly because every time I'd be stopped to chat with a friend when I had it set to stop at 0mph it would pause/unpause/pause/unpause constantly and one time lost the entire previous portion of my recorded map.