This is exciting: a $200 device that turns your iPhone into a color-temperature meter. The closest thing to this is the Sekonic SpectroMaster C‑700R, but that will set you back $1,700.
I’m not the only person who was excited about it: their Kickstarter campaign was funded in just 3 hours today.
The Lumu Power will be very useful in matching a fill light to ambient lighting conditions, for example. Or matching two LED lights, or just for figuring out what color temp the light is under any situation.