Staying in a hotel, I found a place flashing after turning off the lights. Is that a monitor?

It is impossible to install a monitor in a hotel. According to the description, it should be a smoke sensor, which is dedicated to fire fighting.

Smoke sensor realizes fire prevention by monitoring the concentration of smoke. Ion smoke sensor is used in smoke alarm. Ion smoke sensor is a kind of sensor with advanced technology and stable and reliable work. It is widely used in various fire alarm systems, and its performance is far superior to that of gas-sensitive resistance fire alarm.

The smoke sensor has radioactive source americium 24 1 in the inner and outer ionization chambers, and the positive and negative ions generated by ionization move to the positive and negative electrodes respectively under the action of electric field. Under normal circumstances, the current and voltage of the inner and outer ionization chambers are stable. Once there is smoke, the ionization chamber outside will disappear quickly. If the normal motion of charged particles is disturbed, the current and voltage will change, which will destroy the balance between the inner and outer ionization chambers. So the wireless transmitter sends out a wireless alarm signal to inform the remote receiving host and send alarm information.