Hello,

NumptyPhysics does this for its loading a level "live" from the browser (using its "nptp" protocol) . The source would be able to tell you more than I but the gist is that it registers a "mime_open" DBus handler with osso which just loads NumptyPhysics with whatever filename (the File manager passes the file name to the handler; not as an argument. Maemo: making it awkward. ), a mime file installed telling the system about these new file types and entries in its desktop file saying what mimetypes and protocols it supports, what method name it should call when opening the file etc. I've probably missed something but you could look at the source

(The Media player, albeit being closed source, also has such entries in its desktop file)