Answering a doorbell with a mobile phone

Recently, news companies picked up a story about a 13 years old boy who "invented" a 3G doorbell. It is basically a doorbell with a SIM card in it and it calls your phone if someone rings it. I though to myself that this isn’t so much new. Such systems that rang landphones existed for 15 if not 20 years and just a few years ago (probably 5) I read about doorbells that rang a GSM.  Then I dug further into story and realized that, being a kid and not having much money, he build his own system for far less than companies are selling similar systems for (to be fair even less complicated!).

Two main reasons for using such doorbell are:

  • answering to delivery guys when not home and
  • making burglars believe you are home

However. Such system has its flows as well. The boy and his buyers might have already thought of all the situations listed below, but I couldn’t find anything about it.

  • If someone is home, I don’t want the doorbell to spend my money by calling me. OK, this can be avoided if both SIM cards would be on plans which allow free calls between them. 
  • My phone is often turned off so I would miss lots of doorbells. OK, this one could also be avoided by ringing the actual bell in the house and calling the phone simultaneously. So it would work also as a regular doorbell.
  • Door pranks could get to another level. I imagine kids in the neighborhood bothering me (us) even when I (we) are not home.
  • This would allow neighbors (everyone) to call me for free :).
  • If my phone is not available, can it call someone else? Does it ring the next person on the list or can it call just one number. Lets see an example: I’m on the meeting, my wife is in the store, the delivery guy brings the package. The doorbell rigs my phone which is on silent and the package goes back to the local pick up point! No use.
  • What about if someone is home, answers the door while I also answer the phone? This might be a weird situation with me on the doorbell, the guest and the person opening the door. We could have a conversation :).

If it is to believe the story (emphasis on believe), he sold the idea
for £250.000 which is a lot of money. The unit will be sold by retailers
for £40. If everything is true, he has been on the right place at the right time. Even if he reinvented the wheel. Congratulations!