I work from home and this would be cool to communicate with my kids when I'm on a call before they barge in asking questions. HOWEVER, the price is WAY too high. This is at most a $50 dollar thing.
Also, yes I've made signs. It's easy to forget to hang them.
Worked great with my kids for 2 months. Then they got used to it and barged in anyway. The same would happen with this gadget.