I dont own a light meter, but I downloaded an app. I took a quick screenshot to see if this reader looked accurate for those who had a good idea of exposure times. (Of course i would then have to account for reciprocity)
It could be accurate - there is no way to know without having something reliable to compare it with.
Go outside during the day and see how it reads in comparison to what Sunny 16 would indicate. https://en.wikipedia.org/wiki/Sunny_16_rule
That will give you a decent idea of how it performs in higher lighting situations.
By the way, your question is really how accurate the app is on your phone - the phone plays a big part.