Hi guys,
I was looking for an Android app that measures the environment light (and not the reflected light) using the phone’s light sensor. As I currently don’t have my Spyder with me, I wanted to get a hint about which calibration profile I should use while processing 
And it turned out, that there indeed exists an app free of any data-collection stuff and even free of ads. So may I introduce you to LuxMaster Photometer by ReStart Studio (available through PlayStore). Besides the instantaneous lux value, it also offers some nice features for botanists (does my plant get enough light 
), for well-being (do I get enough light in the current situation like office, living, etc. 
).
Perhaps here is someone who also needs something like that - so please enjoy.
Have a good time 
Lars.