OLPC as Datalogger
The OLPC is designed with an audio input that is intended to be used as a sensor input as well as plain old audio. When this is used as a sensor input, the OLPC becomes a datalogger, i.e. a basic tool of scientific investigation. This is consistent with constructionist educational philosophy which says that you teach science by enabling the child to become a scientist.
It is proposed to have data logging features in the Oscilloscope application on the laptop. This would enable children to specify an interval at which to sample the voltage and record it with time stamps. It would also be able to draw a graph of a set of recorded readings. --Arjunsarwal
 Background Information
There is already a thriving educational market selling sensors of various sorts, dataloggers, and datalogging software. Here are some examples to review for background information.
- This page has a list of homebrew sensors built by Lego Mindstorms enthusiasts
- Here is an example of how a little sensor can teach a lot of science (broken as of April 7, 2011)
- World-Stethoscope is a simple V/F converter. It works fine with OLPC Etoys.
- A few IC's that might be useful: