I have a very simple form that is not bound to a business object. I am doing some editing on the fields inside the form, and what to display a broken rule like error message. Is there a way to show that type of message without binding to a business object and setting a broken rule?

You can just use the standard error provider that comes with .net that is what SF is using.

There is also already an error provider on a SF StandardForm.  You can access it through the SetErrorProvider() and ClearErrorProvider() methods on the form.  When you save a business object or call CheckRulesOnRow(), the BrokenRules collection will be populated with the broken rules.  You can cycle through the rules and set the appropriate errors on the text, or you can just create a combined message and show the message to the user.