Well - SPM, and 

* FSL : http://fsl.fmrib.ox.ac.uk/fsl/fsl4.0/feat5/detail.html#prestats
* AFNI : http://afni.nimh.nih.gov/pub/dist/doc/program_help/3dBlurToFWHM.html, http://afni.nimh.nih.gov/pub/dist/doc/program_help/3dmerge.html

I think statisticians don't usually think of sd in spatial terms - I mean - the idea of a Gaussian kernel is a bit different when thinking about probability distributions and spatial kernels - but I might be wrong. 

Your call obviously.