Ten years ago, I would have said this was a product searching for a problem, but now shooting competitively with shotguns of various kinds, I love the idea. This Black Canyon Labs SGS3 Shotgun Safety-Selector uses an AR-style stroke to turn the safety on and off. As such, your thumb can always disengage (and anyone who shoots a cross-bolt safety will testify) engage the safety when dumping a shotgun under the clock. Only one drawback in my mind- it is a 90-degree throw for pistol grips.
The system is shotgun-model specific and is currently available for Remington (870/1100, etc) and Benelli shotguns. The kit is fully ambi with both right and left hand paddles. Rally Point Tactical has the SGS3 available for $125 for either model.