Hackhut user Badwolf recently bought several cheap mechanical watches from eBay. Cheap watches are known to either gain or lose some time each day and he wanted an easy way to tell whether or not they were accurate or not. He used his Pentax GPS camera that had an intervalometer that can take photos every minute for long periods of time.
He set the camera up in front of all three watches he bought and took a photo per minute for 24 hours. Of course, this technique is time consuming, and cumbersome too.
The results of his experiment were that in one day watch #1 lost 24 seconds, watch #2 gained 2 minutes, 48 seconds, and watch #3 lost 24 seconds. He returned watch #2 as not being accurate enough.