I would be interested in:
Bluetooth headphones with noise-cancelling, seperate batteries rather than built-in and foldable.
It seems that the only ones that offer this are the Nokias, and they are very expensive for headphones.
I use the buses, underground and trains a lot, so the noise-cancelling is very useful - even if the noise-cancelling is not the best it will make a big difference to my volume level and hence comfort.
The bluetooth is so that I don't get the cable caught on people and things.
I would also like them to use normal AA or AAA rechargeable batteries and to fold down to fit in my bag when I am not using them.