I know you can use the landing gear as a trigger, but a docked/undocked signal would be nice to determine if you're on planet or docked to a ship - unless there already is one and I'm just not seeing it :-/. You could simply add it as a 2nd signal to the landing gear. You could use it for your critter control sentries (not needed when docked to a friendly ship, but very helpful when on-planet). And you could use an override sensor switch if you dock to an unfriendly vessel and there's 2-legged critters or drones about). Just a thought
There is a LOT more that could be done with signal then is currently in the game; this being one of them. Just be aware that there are currently issues with assigning signals to landing gear: Passing through hangar doors causes landing gear to extend then they shouldn't If you only touch the ground briefly the signal can become stuck in the ON state. This can happen if your flying low and graze the ground or if you hit the ground hard enough to bounce off it.
@Inappropriate - Thanks for the heads up. Didn't know there were issues with the landing gear. Guess I'll just use a standard Sensor switch for the sentries . Appreciate the info!