[Brian]

WH1 - is your iPhone running iOS 4? If so, there's a "due reminders" feature that can be turned on in OmniFocus' settings screen.

If you have the Growl library installed on your Mac, OmniFocus (as well as many other applications) can use it to pop up notifications that you can customize to suit your needs.

You can grab Growl here:
<http://growl.info/>

Do either of those help in the short term?