We have a script (called orawatch) that goes out and looks for different things that happen in the database. It runs every 5 minutes from a cron job. If it finds something that needs to be reported, it sends an email message to a group of pagers. Our Paging carrier has a feature that will convert an email message to an Alphanumeric page.

It took about 6 weeks (on and off) to write the script that does something similar to OEM. You have to ask yourself if it is worthwile to write a program that comes with Oracle for free.