I just found the need for a shutter speed tester. Found this thread and some others in other sites. There's a guy in Romania I think it is, who has designed a low cost shutter speed tester. He's got an entry level model that's only $14.99 on eBay. That one works like with the Audacity program. Then he has a model that doesn't need a computer at all, it has all the electronics inside. Those go for $99 without a light source and $119 with a light source. I think I'm going to buy one of these rather than build one myself.

On eBay, look for seller by the name "vfmoto" if you're interested.