Extremely Short Answer, Updated:
We absolutely do want notifications in OmniFocus, we just want them to be time-based rather than push-based (so they work when offline).
To that end, we implemented calendar-based notifications in OmniFocus for iPhone v1.5.2 for those who are syncing via MobileMe or WebDAV. We create a WebDAV calendar on your iDisk or WebDAV server and tell the Calendar application on your phone or iPod to subscribe to that calendar.
When the appointed time rolls around, the Calendar app on the phone or iPod will present the alert. You need network access when you sync, but it's not required to get your alerts.
If you'd like to know how to use the calendar alerts, visit
this thread. For more info, including what else can be done right now (and an explanation of why push notifications weren't ideal for OmniFocus), keep reading this one. :-)
Longer/Detailed Answer:
The basics: because of (completely reasonable) concerns over battery life, Apple does not allow applications to run "in the background" on the iPhone. This means that OmniFocus has to be in front and running on your iPhone or iPod in order to notify you about some action.
Some folks are probably saying "What about iCal, though? It pops up notifications." to themselves right now. This is true, but Apple hasn't made the code they are using to do that available to third-party developers; we can't use the same method they're using to do this in OmniFocus.
What we really need is a way to send a message to the OS on the iPhone or iPod you're using that says "Hey, at 3pm, when that action comes due? Pop up a message."
The push notification available in iPhone OS 3 takes several steps in the right direction, but is still missing some essential features that we need. The "push" part of the feature name refers to sending messages to the phone from an external server of some sort. For OmniFocus to take advantage of this, Omni would need to run a server which has access to your (and everyone else's) data.
Beyond that, there's an additional problem: just because we sent the message doesn't mean you'd get it. iPod touch users are about half of the App Store customer base; they often have spotty WiFi access away from home/work. If you don't have a net connection, you don't get your notifications on time. That doesn't feel like a good solution to us.
I hope this makes the current situation clearer to folks. We're keeping an eye on this, of course. If some of these problems get solved, we'll re-evaluate. It's very clear to us that there's demand for this feature. :-)
So what the heck do I do now, then?
Well, if you're syncing over MobileMe or WebDAV, one option is to wait for the calendar-based notifications coming in the next release. Otherwise, there probably isn't one clear solution that works for everyone.
If folks only want to use tools on their iPhones or iPod touches, using iCal's notifications seems to be the best solution. (If you're using OmniFocus for Mac, there's an AppleScript in
this post which makes it easier to create an event that matches an action.)
If folks have an iPhone and access to a Mac that they can leave OmniFocus running on 24/7, you can configure
Growl on your Mac to send an email; AT&T will convert that email to a text and send it to your phone. To do this, select the "MailMe" display style in Growl's System Preferences pane; the email address to send to looks like this:
2065551234@txt.att.net
You'll probably want to enable/disable the specific Growl triggers you care about - at the very least disabling "Automatic Backup Created" may be warranted. (Upside: once an event created on your phone makes it back to your Mac, you'll automatically be notified.)
JohnJ80 also helpfully wrote an AppleScript that, when run, uses the free Toodledo web service to do something similar. Toodledo accounts are free, and this method gives you event-by-event control over which actions you get notifications about.
The downside is that it doesn't automatically work for actions you create on the phone; you have to remember to run the script on them once you're back at your Mac. More info is available
here.