Somewhat comically when I went to pick up my boosted board from their shop in Mountain View the guy I met shook my hand with his left hand which I thought was weird, but didn't think much about it.

A bit later I asked if he commuted on his boosted board and he said that he did everyday until recently because he had surgery after shattering his right elbow.

I asked, "Not from the boosted board right?"

He smiled and said he had hit a bit of oil.

Didn't exactly inspire confidence.

I don't really think there's a way to make a skateboard safe at speed. Ultimately if the skateboard stops suddenly, you continue to travel at the speed it was going, and unlike a bicycle, nothing is going to absorb damage except your body.