one way you could do it is if you had the temp file name in a database along with the time it was created, you could just create a function to:
grab everything in the database,
loop through the results,
check whats older than an hour then unlink and delete from the database.
Then all you'd have to do is add this function to a page on your site so its called everytime a user views that page.
its quite a crap idea but it would probably work.