Also available for Microsoft Windows
NOTE: Before running any critical experiment with ESP, we strongly encourage you to test your experiment for a full week, from end-to-end. This includes loading your experiment onto a set of Palms, running ESP with "test" human subjects for a week, downloading the resulting data from the Palms, and examining the data. You'll be glad you did!
The current version of ESP is 4.0.
If you want to modify ESP, you can also download the source code.