I may be late to the starting gate with this but I just read about them in the context of being a comfort for someone suffering the loss of a loved one.
The one I first saw described could be used as a lap rob or shawl and the weight gave you the feeling of a comforting hug. The first one I saw also had weighted hand attached that you could hold.
Further research furnished the information that they have been in use for sufferers with ADHD especially children and they have a good calming effect and help with sleep because they work on the pineal gland in the brain which releases seratonin and melatonin.
Thinking about this made me wonder if they have been tried on people with dementia. I know many caregivers do have a hard time keeping their loved ones in bed at night which greatly contributes to caregiver burnout.
There are several sites where they can be purchased or you can sew your own. the recommended weight is approx 10% of the users body weight and you can purchase weighted polystyrene beads to fill them.
Comforting for both caregiver and loved one