Apparently, the Red Torches are "Always On" emitters, buttons emit a Short On when hit and reset, pressure pads are On While Weighted, and levers are an On/Off Toggle. Wires made of red dust (copper?) carry signals from devices. Also, apparently tracks can be switched now too, by hooking switches/wires up to a track junction. I wonder if you can shoot Levers with a bow to toggle them... if so, I might need to build a target practice track that requires you to hit a series of levers with your bow, or spills you and your minecart into a magma pit.
Some crafty trap ideas I've seen so far:
1) Autolocking Trap Chamber: Since any wire being stepped on breaks the circuit, build an obsidian hall, and use an "Always On" torch -> tripwire line -> metal doors at entry/exit: Invader steps on wire, and breaks the circuit, the Always On signal is interrupted, the metal doors seal and can't be opened, and the prisoner is trapped. Cue whatever flood, sand-fall, or other nefarious device you wish.
2) Landmine Pitfall: Dig a 1-deep hole, and a 3x3x3 pit centered under it. Fill the top hole with TNT, and cap it with a pressure pad, which conceals it with the floor. When stepped on, it activates the TNT, causing it to fall, so the pressure pad deconstructs, and the invader falls with it into the TNT pit, and Explodes. Expensive, but effective.