A wrist-wearable device combines timekeeping functions with monitoring of the radiation dosage to which the user is exposed and of radiation intensity. A Geiger-Muller counter is used as a radiation detector in a wristwatch. A voltage changer changes voltage from 1.5V-3V to 400V to make the Geiger-Muller counter function in wristwatch, by using a voltage pulse converter for Geiger Muller counter power supply. A micro controller is connected to the voltage changer. Switch key control impulses come from the microcontroller; when the signal from the Geiger-Muller counter is received, an additional switch key control impulse is sent. A threshold element is in the transformer primary winding of the compact voltage changer, and is connected to micro controller, while micro controller data bus is connected to bipolar transistor base.