There was a post on the BBGA forum recently on a home-brew kit for monitoring your sourdough culture, it really doesn't surprise me that someone's selling a similar item. It strikes me as information overkill, not that I haven't been guilty of that at times myself.
But most sourdough bakers know their starter about as well as they know their pets, if not better. I can look at mine, and smell it, and know whether it needs to be fed, whether it is ready to be used for making bread, whether it is developing problems, etc.
In fact, I take it back. I know more about how my sourdough culture is behaving than I do about my cat's behavior.