What do I need to sync a local site office SQL Server with the Head Office SQL Server
I ran into a similiar problem for an accounting package. Instead of trying to work out a way to move the SQL data around it proved to be much easier (and more cost effective) to provide a way to remotely access the application. 

I opted for a TS 2008 box.  This includes a large number of international users with terrible bandwidth compared to the states.

EDIT - As syneticon-dj points out there are still potential issues associated with using TS on a satellite link. You would definitely need to look at the latency of your link for a TS solution to work. Some satellite links provide around 300 millisecond latency, others may be over a second.