Not really. It is possible to access the entity manager using JNDI, however this practice is discouraged by jboss and from memory is quite tricky to set up (can't remember why, but I think that you will almost certainly run into trouble). Also you do not actually get the seam managed entityManager, just an entityManager that comes from the same EntityManagerFactory.
Your best bet is to put the appropriate logic in the seam app and use some kind of remote procedure call, either web service based or otherwise to access the information you need.
I am new to seam framework and having problems while I am trying to use the seam catch module from standalone application. I started to wonder it might not be possible. Do you know if I can use the seam catch module from standalone application?