The product link doesn't work anymore, but it has "shoulderflex" in it. A search reveals that it was recalled after a strangulation death:

http://www.huffingtonpost.com/2011/0..._n_938460.html

http://www.shoulderflex.com/

Based on what I'm reading it should be safe for a shirtless person with no jewelry and short hair. You might also keep the plug or power switch handy to turn it off if it starts attacking you.