The images show you how to build them. They are both one block wide and the bottom (upward facing) sticky piston is the piston which detects bock updates.
The first image shows my compact BUD switch design that would send out a pulse and the second images shows my compact BUD switch design that would toggle its output.

But this BUD switch is not bug free, because with some blocks the bottom piston will extend and contract to fast and doesn't take the glass block back down.
I found the following block bugs:

• When the following blocks are placed against the piston:
  Piston
  Sticky Piston
  Repeater
  Chest
  Vines
  Pumpkin
  Jack 'o' Lantern
  Furnace (also when the fire turns on/off)
  Dispenser
  Fence Gate
  Rail
  Powered Rail
  Detector Rail
  Wooden Stairs
  Stone Stairs
  Brick Stairs
  Stone Brick Stairs
  Lever
  Button
  Trapdoor
  
• When the following blocks are removed:
  Sponge
  Jukebox (while playing a music disc)
  
• And when a iron door opens/closes
  

But with the usual block updates it works just fine. Such as glowing redstone ore, or when a torch is placed on/removed of the block adjacent to the piston.