A system operable to determine a future point of time, at which the alcohol concentration in blood of a user is less than a threshold value. The system includes an alcohol sensor operable to detect a current alcohol concentration in blood of the user, and a portable apparatus. The alcohol sensor and the portable apparatus comprises each a wireless communication apparatus. The wireless communication apparatus in the alcohol sensor is operable to wirelessly transmit the current alcohol concentration to the wireless communication apparatus in the portable apparatus.
