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The button represents a single button on a consumer device which acts as both input to a microcontroller (shown in green) and as a main power switch. This is accomplished using an Adafruit PowerBoost 1000C. The output of the SR latch (shown in purple) is connected to the EN input. (SR latch is always powered directly by the LiPO.) When this pin is pulled low, the converter enters a quiescent current state of 50uA as opposed to it's idle state of 5mA. The digital pin represents a digital output from the microcontroller that, when set to high, will immediately reset the latch, turning off the converter.
In this way, a tap on the button can turn on the power to the microcontroller, and then the microcontroller can use the button to detect a long press, which will set the digital output high, which will cut power until the button is tapped again.
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