The high-tech Lumu comes in a little aluminum button can be kept in its beautiful leather carrying case, or hung around your neck like a pretty cool medallion. When you need to measure some light, plug it into your iPhone, fire up the companion app and put it all in front of your subject. Right in front of it, and facing back at the camera. Take a reading and you’re done. The Lumu is — as is the way with all these cool little gadgets — seeking funding on Kickstarter. You’ll need to pitch in $99 to get one.