TL;DRThere is currently no direct way to include the player in the circuit network. But many new applications would arise simply from being able to read a "player" signal from a belt. For each player who stands on a 1x1 piece of belt it would emit a player signal.
Why ?Opportunities for security mechanisms and afk detectors arise amongst many yet-to-be-designed mechanics. Examples off the top of my head:
- Proximity sensor or intruder alert (currently gates allow limited applications)
- Detect if a player may be trying to steal items directly off a balanced in/out flow sushi belt (particularly useful for multiplayer)
- Light displays and dance pads which interact with players walking on them.
- Virtualized circuit-driven games allow for improved player interaction
- Circuit to slow trains down when you are near tracks inside a base
If you have any other applications for this or potential downsides, please share!