Can OS X automate creating a reminders from a page in a web browser?
If you want to add a selected text as a reminder 


Open Automator 
Create a new service 
Service receives selected text in any application
Add a Run ApplScript Action 
Add the following script
Save it


the script : 

on run {input, parameters}

    tell application "Reminders"
        set theReminder to (make new reminder with properties {name:input})
        activate
    end tell

    return input
end run


Now when selecting text, you can with a right clic add it as a reminder. If you want that only in Safari. Replace the any application with Safari at the top of the Automator window. 

And if you don't want to show the Application Reminders when adding a new one, just remove the line  activate in the script.