The only remote options that ModeShape provides out of the box are a generic RESTful service and a general purpose WebDAV service. Sometimes these may be a natural fit, but other times they may not fit terribly well. In that case, I'd recommend creating your own custom RESTful service with an API that suits your domain and scenario. It's so easy to create a RESTful service using JAX-RS nowadays.
Our JDBC driver can be used remotely to query a repository, but you can't really do anything else. For example, we don't support inserts, updates, or deletes.
The other option that may work for you is to allow your clients to start ModeShape locally so it "joins the cluster". Having said that, however, I definitely can see many situations where that not only is not ideal but it is downright undesirable.