A user level forground running process which accepts a cron spec and command which will be executed accordingly. Be sure to wrap the cron spec in single quotes to prevent shell globbing.
$ cronsingleton '* * * * *' notifiy-send "hello"
If you specifiy a file as a signle argument to cronsingleton then that file is parsed as a cron script.
$ cronsingleton mycronfile.conf
TODO: Brief introduction on what you do with files - including link to relevant help section.