As with any app, especially from Google Play

Take a close look at the privacy agreement relative to the app.  Lux may destroy your "personal" data, but may have access to your phone's address book, text messages, etc.  When looking up the URL, there is very little info on the registration of the website.  You don't know who created this thing. I have few apps on my phone because of the data they access when you give them permission in exchange for them being "free" or low cost.