Thanks to designer Hyun-june Yang, hopefully this concept called “Who is out there” will be put into production soon, especially since it does not look overly complicated or requires superior technical knowledge to build. As you can see in the rendering above, “Who is out there” is essentially a peephole for children that uses the principle of the periscope (like submarines) to allow them to look and see who is out there.
Unfortunately this appears to be more of a concept at the moment rather than an actual product, but hopefully parents will start to see the benefits to having something similar like this installed in their front door in the future, especially if they have young children at home.