Planet Waves Humiditrak Bluetooth Humidity and Temperature Sensor. Musical instruments can be easily damaged by large and rapid changes in humidity and temperature. Now you can protect your investment by simply placing D'Addario's Humiditrak with Blustream Technology inside your instrument or case. Humiditrak uses a patent-pending Bluetooth sensor to provide a constant stream of temperature, humidity, and impact data to the free smart phone app to alert you of hazardous conditions that can lead to diminished playability, costly repairs, and lost value to your instrument. When Humiditrak detects dangerous conditions, push notifications are sent to your device allowing you to take corrective action before damage occurs. Cataloging and monitoring a collection of instruments is so easy and convenient, you'll want one for every instrument you own!