This isn’t my exact invention so please try and refrain from giving opinions on its success.

Anyway, would it be possible to create a simple bracelet with a “tracker” inside that doesn’t actually track location, but instead is able to track each time a person goes in and out of a doorway. For instance, if I wanted to check how many times each person in my household is going in and out of my front door, could I have us each wear a bracelet then equipment some kind of sensor to the doorway and have this all be tracked.

If I wanted to create this invention, how much would I be looking at full cost?