Virtual Belfry (starting with version 3.3) supports control switches that connect to a commercially-available board called the DigiBee, pictured above. This can handle up to sixteen digital inputs and connects to the computer via any free USB port using a standard USB cable. Note that this board has been found not to be suitable for bell sensors, due to its 50ms minimum cycle time between successive checks of pin states. This is too slow for reliable detection of signals from a sensor attached to a bell wheel, or for accurate reporting of striking performance. It is, however, suitable for foot-operated control switches.
This board is available from https://www.pc-control.co.uk/control/products/boards/digibee.php
Instructions for connection of this board are provided in the Help file that is part of the Virtual Belfry setup, and a detailed manual comes with the board itself.