A reflected light meter with spot metering (using the device's camera) and an incident light meter (using the device's light sensor) in one app. Tested accurate against Gossen and Sekonic meters on most devices.
Can be used for any type of camera from film SLR to pinhole to cinematographic.
In addition to the two meters, the app includes a Color Temperature (White Balance) meter, a Reciprocity Calculator, an Exposure Convert, a Manual (Sunny Sixteen) calculator, a Depth of Field calculator, and an EXIF Reader.