I've used the Burris "SpeedBead" on an Extrema II (like the one pictured in the above post) and the very similar looking Burris "FastFire" on a Sako rifle.
Both were surprisingly fast and simple to use. Hadn't actually considered one on a shotgun, but what a great sight for either turkey or deer hunting. Even suitably impressed with how well it worked when shooting a round of 5-Stand (clay targets) with it ! On the Sako rifle, couldn't imagine a quicker set-up for close-range shooting. Very small & compact, easily operated on/off switch and a piece of cake to take on or off the rifle if you need to.
The shotgun SpeedBead mounts easily enough by removing the stock and fitting the supplied mount into place between the stock & receiver....the rifle intended FastFire is even easier on a standard Weaver-type base. ( Also an option for a shotgun with a weaver style base or a cantilever) Last I looked, no problem mounting the SpeedBead on the various Benellis ( 3 different mounts), Berettas, Remington 870, 1100, 11-87, Franchi I-12, Stoeger 2000, Browning Silver or Browning Gold/Win. SX3.