Here’s the hearing impaired doorbell hack that you may find helpful for someone who’s having a problem of not getting a fully functional solution with commercial off the shelf hearing impaired products. General idea of this hack is to be able to see lights flashing in the multiple rooms at the same time. A possible upgrade of the solution would be to have additional sensor (movement, noise) that is able to give input about people presence in the room and thus make a system rule for which rooms to flash the lights.
On the same website you can find many useful tutorials, one of which is the Internet of things class.
