People have been trying to find ways to do this for a long time, and it is finally here! Today I will walk you through step, by step, on how to transmit an invisible block updating signal through up to 18 layers of blocks!

1. Place two tripwire hooks facing each other, they cannot be more than 18 spaces in between them.
2. Build your favorite BUD or T-BUD on either end, with the piston in contact with the block the hook is on!
(A BUD will emit a pulse when the wireless signal is sent, a T-BUD will toggle the state.)
(http://www.minecraftwiki.net/wiki/Tutorials/Block_update_detector)
3. Place a repeater facing the are in which the BUD will push its block, then a torch behind it.
4. Place a redstone wire on the opposite side. (This is your output!)

When EITHER of the hooks are right clicked, your BUD or T-BUD will be set off.
If you are having a hard time with this, here is a download.
http://www.planetminecraft.com/project/wireless-redstone-signal-even-through-walls-12w22a-964384/

(NOTE: This will only work in 12w22a, or the 1.3 update, if and when it comes out!)