I am beginning to work on a research project that involves windows mobile and other things. Here are some good references on writing communications related stuff for windows Mobile

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnnetcomp/html/netcfSendSMS.asp

http://msdn.microsoft.com/library/en-us/dnnetcomp/html/httpcomm.asp?frame=true