A device in one example comprises a standalone universal serial bus keyboard emulator and an ultrasonic sensor component. The standalone universal serial bus keyboard emulator is coupled with a computer through a universal serial bus port. The ultrasonic sensor component is coupled with the standalone universal serial bus keyboard emulator. The ultrasonic sensor component communicates one or more signals to the standalone universal serial bus keyboard emulator that serve to allow the standalone universal serial bus keyboard emulator to make a determination of entry to or exit from a predetermined proximity of the computer by a user. The determination of entry to or exit from the predetermined proximity of the computer by the user causes the standalone universal serial bus keyboard emulator to send a corresponding entrance or exit user configurable keystroke sequence to the computer through the universal serial bus port.