See the video presentation from the recent Phaedrus Systems Technical Seminar.
https://www.youtube.com/watch?v=6sQpGwUez6g
Test & validate requirements in natural language
Stimulus is a simulation environment to test and verify requirements in natural language. This tool is aimed at the critical systems market as it is underpinned by formal methods but it is very useful for agile developments with rapidly changing requirements. Requirements can be validated quickly before any design let alone coding.