I want to submit this library for consideration to be included in gearbox. It implements segment-based EKF localization:
"Mobile Robot Localization and Map Building: A Multisensor Fusion Approach"
J.A. Castellanos and J.D. Tardós
Kluwer Academic Publishers, Boston, 1999
ISBN 0-7923-7789-3
svn diff taken from the 'submitted' folder against current trunk