Besides the obvious (buy OF for iPhone), for text items you can use the
send-to-omnifocus@omnigroup.com email service. Send an email to that address, in plain text, with the subject line as the action name and the body of the message as the note. In a few seconds, you'll get an email back with a link that, when tapped on a device which has OmniFocus installed, will open OmniFocus and add that action via the Quick Entry form.
You can see some screenshots in this thread:
http://forums.omnigroup.com/showthread.php?t=23572