Yes BH505 is the only option.
But one personal suggestion for you, even I was very keen to buy a bluetooth neck headset a long time and I bought Motorola S9 as BH505 was not there that time and I tell you its a waste of money,I hardly use them they are just lying in some corner of my room where I just to dump all the crap, its very difficult to wear them all the time and they are also very delicate.So I bought a Meelectronics M6 and now I use M6 all the time.
So if you want a bluetooth in your headset then get a bluetooth earphones there are plenty of models available in market from sony ericson,nokia etc
If you want then I can suggest some specific models