135-hour-battery-life skin temperature monitoring system using a Bluetooth cellular phone

In this paper we present a long-term temperature monitoring system that uses miniature wearable sensor nodes that connect via Bluetooth to a cellular phone in a star topology. Monitoring of skin temperature over multiple days has been shown to be useful in clinical research related to metabolic and cardiovascular diseases, and it has a potential role in the study of circadian rhythms in patients with cancer. The system can provide immediate remote feedback through a phone´s internet connectivity and eliminates the need for a dedicated base station. By utilizing Bluetooth in a burst-mode regime, sensor nodes can work autonomously for 135 hours at a sampling rate of 0.2 Hz. A validation study showed that the system can reliably record circadian temperature rhythms in an ambulatory environment, and can serve as a sensor platform for novel applications.