Merging two similar threads asking the same question, retitling the merged thread to make things a bit more findable.
Yep, OmniFocus for iPad and OmniFocus for iPhone can sync with each other; the Mac app is not required. You'll need someplace to store your sync data, and then the two devices can sync with each other via WebDAV.
(iOS devices can't be their own sync server the way a Mac running OS X can, so Bonjour sync is only an option if there's a Mac in there somewhere.)
The easiest way to get up and running would be to head over to our Omni Sync Server page
and set up an account. When you do that, the server will send you an email which contains a link you can use to set up both versions of OmniFocus to sync with each other.
Just install OmniFocus on each device, open the email the server sent, and tap the link. OmniFocus will launch, ask if you want to replace your sync settings, and set everything up. If you have existing data in one version or the other, you'll want to start with that device; from then on, though, you should be good to go.
(Note that if you do have a MobileMe subscription, your iDisk will work just fine for storing your sync data, as well.)
An added advantage here is that you'll be able to sync either device any time they have an internet connection. You don't have to sync all your devices at the same time.