wrap external code

Is there an easy way to wrap a pre-built app/codebase into a drupal node? Say I have this external app that runs under, lives in, and uses it's own dir name for all its path processing etc. Can one easily import this code into the drupal codebase and easily wrap it's output under a drupal node? For example:

http://myserver.com/my_app_here - core functionality is based of my_app is based on this path - servername

to:

http://mydrupalserver.com/?q=my_app_module

or

http://mydrupalserver.com/node/my_app_nodename

What do I need to do?

Thx,

Gerry Lawrence