As mentioned. I've used it a couple times and still prefer old school methods, but has actually worked for me. Wasn't great for plaster and lath walls, but I think there's been some updates and may be better now...
Here's a video on it:
Mine didn't come with an iPhone cable, so if you're an iPhone user, please check for compatibility (make sure there's an app in the iPhone app store).
50$ obo
Thanks,
David