Bluetooth Humidity/Temperature sensor with free iPhone app. No need to open your instrument case to see the humidity/temperature readings. You can view the information on your iPhone. Free App download available from iTunes stores. Search for: HT Tracker Once you have downloaded the App, place the sensor on the iPhone screen and press the + sign on the upper right corner of the screen to sync with the App. Set humidity/temperature limits and your smartphone will alert you if the readings are too high or low. The App can read up to 7 sensors and has a transmission range of over 100 feet. Sensor comes with clip, so you can attach it to your instrument case. You will be notified of App updates automatically.