I asked a speaker at javaone this same question. His response was to use web services.
Seemed to me also there should be a more elegant(SIMPLE) solution to this.

First of all, it kinda matters ;)
When you invoke EJBs on another type of application server, most of the time
you've got to use a kind of bridge. In my work we use applications on JBoss
2.4.7 and JBoss 3.2.1. Believe me, you can't just invoke method from the
EJB. You've got to configure a bridge between them. I won't give you details
here simply because I don't remember them, but it's not that easy.
Any about the dynamic thing ... Make it dynamic on the application level.
Create a table in your database that contains the properties and select from
it every time you want to connect to ejb deployed on the other server. This
way you won't have to build your application every time the address changes.

Regards

The automatic dependency discovery relies on JNDI.  It's not magic.
However, to get a remote app server's beans in the right places will
probably require some vendor-specific configuration info.

Let's say you have a session bean named com.example.HelloWorld with a
method
@EJB
public void setMessageProvider (MessageProvider provider) {...}
through which a second EJB (implementing MessageProvider) is
injected.  When the container goes to populate the properties of the
HelloWorld bean, it looks up the following JNDI name:

   java:comp/env/com.example.HelloWorld/messageProvider

and, if it finds an object there that implements MessageProvider, it
injects it.

There is a little bit of extra magic involved when there is a
MessageProvider-implementing bean in the same application: the app
server is required to automatically map it to that name because its
interface matches the required interface of the injection target.  You
can do a lookup for that name in your code yourself and find the
MessageProvider there, if your server follows the rules, even if you
never explicitly told anything to put it there.

Nothing about injection *requires* that the MessageProvider object at
that name be from the local container, though.  Using container-
specific configuration you can put any object you like under that name
in the right namespace, at which point injection will pick it up and
use it.

The real problem is mapping an external server's EJBs into the
java:comp/env/ namespace of the right EJB on the local server.  Since
you haven't specified which server(s) are involved, I can't offer you
anything concrete beyond "check the docs" and look up "remote jndi" or
"federated jndi" to see if there are any clues there.

-Owen