I've never heard of such a thing being possible, and while I can't definitively tell you that it can't be done, I'm just going to say it can't be done because I don't think any phone supports the Bluetooth headset profile to be used, well, as a headset. The headset profile is used by headsets, computers and other handsfree devices (like in cars).
...I just took a look at Super Bluetooth Hack, and it's a Java application. I'm not exactly able to figure out how it works since my Omnia doesn't have Java at the moment and I don't have any other dumbphones with Java capability, but I'll look into it. Bluetooth is notoriously fickly and I've never had great luck with it beyond pairing to the car's handsfree system, but it does work on the Omnia, I know that much.
Also, don't be discouraged if nobody responds to your post; as Blazingwolf said, leaving a forum filled with very friendly, knowledgeable and helpful folks and lots of information just because one question didn't get answered is not a great reason. I would be more discouraged if I got posts in my thread that said nobody knew the answer to my question. Stick around, you're bound to learn a lot about this phone!
