It’s definitely an interesting question! A lot of people would like to see this. 
This concept is generally called microlocation, and it turns out to be very tricky to pull off. Most technologies transmit through walls (including I beacons) , Making it very difficult to define a “room” the way humans do. At least unless you include at least three devices per room, which increases the cost considerably.
And then there’s the issue of what is being detected. If you require the person to carry the phone around with them, you really limit its practicality. Smart watches or other wearables may eventually provide this but again there’s that room and wall issue.
Many experts think that we will get to a point in a few years where we have devices that recognize heartbeats, but we’re not there yet.
There are several companies working on this. Logitech has invested in one, but it still requires you to carry your phone with you. 
There’s been quite a bit of discussion in the forums about various microlocation approaches and technologies, and some really creative ideas . The following thread brings together most of them, so I would start there.