A beehive (and not only) monitor (temperature, atmospheric pressure, humidity and noise level) the size of a box of matches.
iTRUBEC Minimonitor started as a side project to another our project – iTRUBEC – beehive heating – published recently. The objective was to build a tiny device capable to monitor beehive (and not only a beehive). The result is matches box sized device with WeMos D1 mini, BME280 and MAX4466 in it and two additional DS18B20 sensors connected via two extra wires.
iTRUBEC Minimonitor v1.0 – IoT for Bees – [Link]