I know many of our mobile partner community are out there connecting Windows Mobile to SBS so though you may like to kno wthta th e The Official SBS Support Blog is now live. "This site will host technical articles and discussions regarding a wide variety of SBS-related topics" It promises to be a great resource.
SBS 2003. Makes a great platform for mobility.
All the building blocks are included, to setup a mobile backend system fast.
Having ISA, SQL, Exchange etc.. on one box makes deployment a breeze.
+ the wizzard configuration makes complex operations very simple.
Richard (Anglia Business Solutions)