Product review (2 stars): D'Addario Humiditrak - Bluetooth Humidity and Temperature Sensor
I am unable (more like unwilling) to download the necessary, free D'Addario Humiditrak app (via Google Play Store) to my phone because it requires everything to be made available for access that you have on your phone - files, photos, microphone, location, etc...  I don't believe any of those are necessary for this app to work and I loathe allowing anything or anyone access to my personal information.  I won't download any invasive apps to my phone and I deem this one to be very invasive. All it should only need is wifi and bluetooth access.

The D'Addario Humidtrak device might work perfectly wonderful at detecting the level of moisture (humidity) surrounding a 1699 Stradivarius violin but I guess I'll never know unless that app is made less invasive. Until that occurs I will just continue to check the humidity using an old fashioned barometer.