The home monitor based on the Beaglebone can measure and report on two temperatures and one A/C power present signal. The external circuitry required to do this includes two negative temperature coefficient temperature-sensitive resistors and bridge resistors, some optical isolators, a wall wart power supply (for A/C detection), and a special circuit that uses one Beaglebone GPIO output bit to switch on and off the +5V power line in the USB connection to the Option Icon modem, simulating plugging and unplugging it under program control. This is to correct for some obscure problems where the modem times out and seems to require power cycling to fix.
The USB power switch also uses a separate power supply for the modem, so it acts sort of like a powered hub, and has plenty of power. (Limited power is a chief suspect in a previously reported problem where the modem would stop working very frequently.)
I actually have this stuff wired up on a couple of breadboards, mounted with the Beaglebone on a piece of foam. Might see about making a PC board (shield or whatever Beaglebone people call the boards that mate with the Beaglebone external expansion connectors.)
I published an informal hand-drawn schematic in the last post here. This is a better schematic of the support circuitry that does this:
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