I have been experimenting the last couple days with a wearable electronics project – a wireless body temperature monitor/logger. The idea is to remotely monitor kids body temperature, if they are sick, and put up a status display with alarm function in our bedroom. The remote monitor will be another Funky with RGB LED for visual temperature representation and a OLED display with a piezzo buzzer to sound alarm, if the temperature goes above a threshold. Since the transmissions are picked up by my IoT gateway and logged to emoncms, I can visualize that data remotely, including on my phone. Body temperature data is collected and transmitted wirelessly by a Funky v2 equipped with a DS18B20 temperature sensor and a CR2032 battery holder (extra flat one). I soldered a 0603 sized 4.7K resistor on the DS18B20 (required for its operation), pictured below (really miniature):
The wires were then covered with heat shrink tube:
.. and the sensor soldered to Funky’s pads:
Using an extra-flat CR 2032 battery holder to make the project as thin as possible, and it measures only 9mm:
I weighted the complete project (with battery inserted), it measures barely 8 grams:
The node is running the DS18B20 sketch; I wanted to stress-test it and am sending data every 5 seconds. The final project will send once a minute.
My next challenge was to attach it to my body. I originally tried to have it on my wrist using a stretch band, but the temperature of the wrist is a bit low (normal):
I could add to the reading to compensate for this. I tried another place, just taping the sensor to my arm:
The temperature sensor goes under my arm.
I had it running for the day, I was doing gardening, lawn mowing and at some point was away from home. Below is a chart of the readings:
Obviously the position of the sensor isn’t optimal, I would get all sweaty when mowing outside in the intense heat (resulting in dropped temperature readings); I even took a shower with the sensor covered with a dry towel. Measuring temperature under the arm requires it to be firmly pressed to the sensor, while I have my hands moving around all the time, resulting in falsely low readings. Maybe I need to try another location for attaching the sensor. Below is an infrared image of a human body (taken from here) 
Overall interesting project with potential for use.
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