It not a flash but a fill light right? I think its pretty cool. I think it will attract attention which might be good and bad. The major issue i would worry about is uneven light. So if you shoot from the hip, maybe the face is not well lit, but the body is..
Anyway, very interesting and I can't wait to see the results. A 21 mm at night with flash is so much fun, but flash does give away the moment....