I use the original Jawbone with my phones. I expect it will work with the N900 as most headsets will. The noise cancellation seems to work when I'm talking with lots of background noise.

There's a Jawbone 2 out now. I think it's slimmer. I think cnet.co.uk had a review at some point.

I don't have any bluetooth headphones for music, so I can't help out there. I tend to plug in speakers via the 3.5mm jack into my N82 or Blackberry Bold at work, when I want to listen to music.