How is your network set up, are you behind a router, for example? If you are behind a broadband router, you would just have to forward the correct ports (80) to the public internet... potentially exposing your Empeg to attack though. You could also place your Empeg's ip in the DMZ for your router also.
From a handheld - well, the browser would have to support the correct features like XMLHTTPRequest, and I do not think either Web Pro or Blazer does. Maybe Pocket IE, but not sure. The vanilla Hijack web interface would work, though. Your problem is just how to connect the handheld to your network.