Small, inexpensive, and easily-assembled () wireless multi-sensor that is powered by a CR2032 button cell. Compatible with MySensors. The PCB is a circle whose diameter is 29.16mm. Most parts are optional, and only a very few parts are required. For temperature alone you can use the temperature sensor built into the nRF51822 chip itself. For greater accuracy and/or humidity measurements, you can add a Si7021 or BME280 or other I2C sensor using a 4-pin SMD Header (see BOM for links).

Pads are provided for installing an optional Hall Effect sensor (which can detect magnetism) and also for an optional light sensor and/or acceleration sensor. See BOM for details.

By adding 3 (optional) pairs of male header pins, the sensor can also serve as a water leak detector. The pins will form a tripod for the sensor to sit on, creating stable support and helping to elevate the sensor above a water leak. The device can be programmed such that if adjacent support pins contact with water, it will wake the sensor, which can then report the event to a gateway and thereby trigger an alarm.

For PIR capability, you can simply plug it into this PIR module: https://www.openhardware.io/view/420/AM612-Passive-Infrared-Sensor-Breakout-Board