... these inexpensive little sensors and other chips with very simple wiring to sense and control the physical environment. The interface is very flexible -- everything from a web browser, to read and writing directly to the chip's "file" to integrating with your programs -- even over the internet.
There is a growing number of 1-wire sensors: temperature, voltage, humidity, light, ultraviolet, pressure, thermisters, thermocouples, programmable microcontrollers, relays, lights, LCD panels, etc