You could have your Pocket PC "push" the data up to a web service, then have
the service transform the data in whatever way is needed, and then stuff the
data into the Oracle db. This way the web service acts as an abstraction
layer over your backend server data source. "N-Tier"ing your way through to
the database gives you greater long term flexibility in your app. If you
change from Oracle to SQL Server (or even Access, flat file, XML, etc), then
your client (Pocket PC app) will not need to change as it merely spits data
at a web service on the server.
If you want Oracle to "pull" the data from the Pocket PC, as far as I know,
you are on your own with this. You would have to write some code to listen
on the Pocket PC and respond to the request. But I don't believe that Oracle
and SQL CE are going to play nice together.
Typically the Pocket PC is going to be your client, so unless it is
absolutely necessary, you may want to look into pushing the data up to the
server via web service.