I too am dying for a viable iPhone interface that does not rely on a web-based solution...but in the meantime, I just had a thought. I am primarily using iGTD, but this should work with OmniFocus as well if it is synchronizing with iCal & .Mac. Check out the following site:
http://iphoneigtd.com/
Enter your .Mac login....
The big problem is that it is read-only, and you can't update tasks on the fly, but you can see 'em.