To add to authenticity, I have purchased from a tear down yard a genuine B-737 trip reminder indicator. These indicators are installed into the right hand side of the captain's yoke. Initially used as a method for the pilot to remember the flight number of the flight, they were rarely used and eventually phased out of service. The pilot uses his thumb to move the three segmented dials to indicate the flight number. I believe when flight numbers began moving into 4 digits these gadgets were replaced with 4 digit indicators or there use discontinued.
I will use the indicator as a prompt to remember the landing speed (VREF). After I have calculated VREF (manually or with the CDU), I thumb the digits into the indicator. This acts a backup to looking at the PFD display. At night the indicator is back lit. The interanl light plate (bulb) is powered by 5 volts.
Although the trip reminder indicator is a very small add on, it's pieces if equipment such as this that provide an added level of authenticity when constructing a simulator.