select * from v$session where [program|module|client_info etc] = <some identifying feature>
where schema = 'myschema'
1: it is quite simple to create another user and grant privileges and create synonyms on your schema to bypass user/schema counts.
2: If your exe is renamed, the 'program' column doesn't work either.
If it iss licence management you're after, I'm afraid things a are possible but a little more complex.
Please don't email me directly with questions. I've probably just got home from the pub and cannot guarantee the sanity of my answers. In fact, I can't believe I actually made it home.