What it does you stick it over your switch and control the switch with your phone some mechanical device switches the switch off and on. Pretty interesting approach.
Curious is there any esp8266 based variants of this device they are all just direct communication through bluetooth it seems or something.
I could see some obvious pitfalls like batteries potentially being an issue depending on how it is done and how often they need to be changed but could be an excellent thing for people not willing to wire things in due to obvious risks and concerns or lack of know how.
Where I buy my ESP8266 boards from... (Banggood)