[jloughry]

See https://en.wikipedia.org/wiki/1-Wire

"One distinctive feature of the bus is the possibility of using only two wires: data and ground. To accomplish this, 1-Wire devices include an 800 pF capacitor to store charge and power the device during periods when the data line is active."

You can buy devices that put an entire JVM inside a two-terminal component, of similar physical size.