More advanced Cron handling was added to Tiki6
http://sourceforge.net/p/tikiwiki/code/HEAD/tree/trunk/tiki-batch_todo.php
Next step is to have it web-based like Drupal's Poormanscron
TRIM could also be used to launch it...
See also: Workers
Related links
batch job | batch process | Cron job | Cron tab | Cron | Scheduled Task