I don't know of anyone who has one, but from the images I've seen it appears to be something that essentially makes the crack a part of the design. Most dashes crack where the material thin around the airbag door, and these plastic covers have a very clear line around the airbag so it doesn't impede deployment.
In my opinion, unless your dash is cracked six ways from sunday, those plastic caps don't improve the situation. Sourcing a new dash is the better way to go to achieve that goal. After buying my house, I found an uncracked Deep Slate dash in a Special at a Detroit salvage yard and took it home to keep for that rainy day if and when my factory dash cracks. I'm continually hitting it with 303 protectant, keeping it in the garage, and using a covercraft fitted sunshield whenever the car sits outside, staving off that eventuality.
2002 Chrysler 300M Special - Deep Sapphire Blue/Storm Gray Metallic - 142,000 miles