You surely know this feeling when the doorbell rings while you are doing something interesting: watching a movie, playing a video game, or spending a romantic evening with your loved one. And when it turns out that this is an uninvited/unwanted guest, you get even more pissed off. Of course, you can ignore it and not open the door, but there will always be this hint of uncertainty – “maybe it was important”. The solution to this problem is the “smart doorbell”. Thanks to it, you’ll know if it is worth getting up from the couch and opening the door or not.