Figure one shows the idea in a physical mock up. Actually, the parts are real, they just haven’t been soldered together yet. So, we have a battery bank of three Imedion NiMH “AA” cells, running between 3 and 4.2 volts and feeding a booster which supplies 5.0 VDC to the development board. We have the Photon (of course), and an ADC board (or other board) for sensor measurements. Did I mention that the Photon, in addition to WiFi, does I2C (1), I2S (1), SPI (2), ADC (8), DAC (2), UART (2), PWM and multiple general GPIO? For $19 bucks?