Obvious use cases are entering a room while carrying a child, or when your hands are full of boxes or bags of groceries. If the wrong commands are used, the device could become confused, which could then lead to some aggressive stomping and loud yelling, which could lead to further confusion.
Anyway, it will be an interesting experiment for those that choose to purchase a Listnr, providing the company reaches its funding goal on Kickstarter. Personally, I am not convinced that I need one of these in my life. One final feature is that it can analyse voices, so one obvious application would be to use it as a baby monitor. I'm not sure, however, if parents are crying out for a machine that tells them if their child is happy or sad based on the noises they make!
If you'd like to pre-order one, the regular price is $199 (£129), but the early bird discount of $99 (£64) is still available. The estimated shipping date is August 2015. International shipping will be offered for an undisclosed sum.