... I bought an OLPC XO-1 <http://en.wikipedia.org/wiki/OLPC_XO-1> laptop through the G1G1 program <http://laptopgiving.org/en/index.php> and was intrigued to discover the Measure <http://wiki.laptop.org/go/Measure>activity. The measure activity uses the internal audio system to measure a value input on the microphone socket. With nothing connected this application reads the value of the internal microphone and displays a waveform. You can have fun just by whistling, speaking or singing with Measure running. But since you can measure a voltage input into the microphone socket, it's possible to build sensors and connect them to th OLPC XO-1. On the Measure web site they mention building a simple temperature sensor<http://wiki.laptop.org/go/Measure#Let.27s_measure_Temperature.21_.28_Featured_activity_of_the_month_.29>using an LM35<http://www.jgc.org/blog/2008/03/building-temperature-probe-for-olpc-xo.html>temperature sensor that looks like this: ... http://blog.makezine.com/archive/2008/03/make_a_temperature_probe.html?CMP=OTC-0D6B48984890 -- http://olpc.ellak.gr