This is to be used on your key ring or things you carry with you. The only important thing is to make sure your hub can detect your sensor from where you need. Imagine an old house with thick walls or your hub is somewhere it cannot easily reach the arrival sensor, then the performance will not be good at all. It already struggles in ideal conditions. I prefer using the mobile phone detection which is based on your phone location and it directly use your data connection to indicate to the hub you are here or not. However, this is not as accurate as the arrival sensor.