Bukkit

I think there should be sensor signs too.
Such as a day sensor:
[LogicSign]
DAY

Turns on during day,  (Implemented in my Fork!) (!DAY for night. :))
long time=sign.getWorld().getTime();
variableMappings.put("DAY",(time>0 && time <12000));
This code has been tested to work, Ive also submitted a pull request for it. (I will be exploring the options for the other sensors later)

And possibly proximity sensors?
[SensorSign]
proximity
player    (Player or mob)
5  (Distance to check)

[SensorSign]
proximity
mob
5