Just discovered these things. They're triggered optically by the on camera flash, and they fire. I could see the problem if there were several photographers around, but otherwise, those seem almost too good to be true for the price. I found quite a few for $20-40 each. Seems like you could buy a handful of those and just be set for your off camera lighting needs. Questions for anyone who has/uses these. How reliable are they? Are they worth the money? Do they work well in already bright conditions, like full sunlight? Like I said, for the price, these seem almost too good to be true, so what am I missing? Thanks!!