KLM stands for Keystroke-Level Model, a hard science approach to human computer interaction, based on GOMS, developed by Card, Moran & Newell, and spelled out in their book The Psychology of Human Computer Interaction, 1983.
It is designed to be easier to use than other GOMS methods, such that companies who cannot afford HCI specialists can use it.
The CogTool project has developed an open-source tool to support KLM-GOMS analysis.
External Link
GOMS Analysis Techniques - Final Essay