Product review (4 stars): Must have the app to function. Works great and is cool to monitor the conditions your guitar/piano is stored in.
This item works great with its intended purpose. Set up is very simple.  You'll need to download the Humiditrak app to use this device.  Once you download the app, you'll remove the battery strip and may have to (I did) reset the battery my placing it in the correct spot. Once your device is ready, syncing it with your phone is very simple and takes less than 5 seconds.  You can custom name your instrument, but this device is targeted for guitar and piano rather than ALL musical instruments.  You can select an icon so if you have multiple instruments you can quickly and easily check in on the status of the temperature and humidity conditions your instrument is in.  I'm not a die-hard musician, but this is a great idea for those looking at keeping their instruments in conditions to last longer to avoid deterioration.  I'd say this is more for the collector's to monitor and extend the life of their instruments.