Here's some early screenshots of the Observer Trap- variations on this trap will be found at the top of the Jungle Temple.
-Contained inside an obsidian casing is a barrel filled with loot. eight dispensers are inset into the ceiling in a diamond pattern, and observers form chains observing the blocks that make up the casing. Breaking any of the observers, or the obsidian blocks surrounding the loot barrel triggers a central circuit, which activates all the observers: Dispensing lava buckets and four tnt into the chamber, and two additional tnt in the ceiling; destroying the circuitry and the loot.
-Breaking the dispensers triggers observers hooked up to them, which also activates the circuit. Each dispenser also has a comparator hooked up to a redstone torch; emptying a dispenser thus deactivates the comparator, activates one of the torches, and triggers the main circuit. (Again, activating the trap.)
-Coming in from the ceiling is also a challenge- in addition to pressure plates hidden inside the circuitry, a pattern of four observers observing the ceiling blocks can also activate the trap. (Which, again, destroys the treasure, and likely kills the invader too.) In addition, the comparator system means that cutting any of the live wires inside also activates the torches, and by extension, the lava and explosives.
I had my brother unwillingly playtest this, and he eventually came across a rather Temple of Doomy solution; to trick the comparator system, you have to carefully place another item into each of the dispensers, and then remove the lava and tnt- messing up any of them activates all the remaining dispensers, so you have to do so carefully.
Once the main dispensers are deactivated, you can drill in from the top, remove the last two tnt, and then safely disassemble the circuitry. As far as I can tell, there isn't actually a way to disassemble the observer/obsidian cube without triggering the trap.