I'm wonering who would go through the expense of the site when they don't have a product to sell yet? I guess it might record the number of bubbles per minute- but that really isn't hard to do anyways. Guess I'm just thrifty!
I would question its accuracy. There are other factors beside fermentation that will cause CO2 to leave or not leave the airlock. I would stick with the tried and true (mostly) hydrometer.