I know im going to catch some heat because of this but the majority of the apps will not be accurate at all. Besides LUX is not a good way to determine light intensity on a reef tank because Lux is a standard that measures perceived brightness in human eyes and will not accurately measure the heavy weighted blue and near uv range spectrum that corals actually use.
This does not make it an accurate measurement for reef tanks. You can take two identical tanks, one with a radion measuring 400 lux and have corals thriving and one with a sodium vapor or hot light studio light that lux is actually designed to measure at 10,000 lux and the corals would be dead in a week.
If you already have a Seneye that does accurately measure spectral data and PAR I would see if you can borrow a laptop or other device and use real, quantitative data that accurately measures the light quality that corals need.