Actually there are many darkroom items that can be affected, but as pointed out the effects will not be detected.
Some examples: The ECU1840 controller for the Durst L1840 times off the mains and the power supply needs to be set to 50 or 60 Hz for proper operation. The signal is carried through the ribbon cable on one of the outermost wires, so if the enlarger runs over the cable, the timer can go out (ask me how I know...). Also, zero crossing detectors are used for timing in the main lamp regulation circuit but small frequency shifts should not make any difference to that circuit. The Omega D5500 uses a 6MHz crystal for timing so it would not be affected.
As mentioned the Wejex sensitometer uses a stepper motor, as do the Graylab 300 series timers.