The JAGS-Wiener module by Dominik Wabersich and Joachim Vandekerckhove extends JAGS by adding the distribution “dweiner” for the the first passage time of a drift diffusion process. As far as I know, this is the first third-party JAGS extension that is distributed as a standalone module [1]. You can download the source code from sourceforge, and for Windows users, there is a binary installer.

Dominik and Joachim have documented the process of putting together the JAGS-Wiener module in a tutorial article, which is now submitted to Behavior Research Methods. This article fills a much needed gap in the documentation, and will hopefully encourage others interested in extending JAGS to follow suit.

[1] There is also the lossDev package for R, distributed via CRAN, which also includes JAGS extensions. This is a little different as it is tied to the R interface.