My Uncle has since spoken to Sony Ericsson who have confirmed that it
is not possible to activate voice dialling via the magic word over a
Bluetooth headset. It is however possible to do it via the wired
handsfree kit supplied with the phone. There are however also issues
with using voice control to hang up or cancel a call you have dialled.
It looks like the technology still has some way to come before it is
truly handsfree.

google@mr-jenner.co.uk wrote:
> Hi,
>
> My cousin recently purchased a Sony Ericsson K800i primarily because of
> the 'magic word' activated voice dialling. She is quite disabled and
> so button operated voice dialling is very difficult. My Uncle has
> managed to get the 'magic word' operated voice dialling working with
> the phone but is unable to get this functionality to work with a
> Bluetooth headset.
>
> Essentially what I would like to happen is.
>
> - Have the phone setup for voice commands and magic word activation
> along with being paired with the Bluetooth headset.
>
> - My cousin says the magic word into the Bluetooth headset (without
> pressing any buttons)
>
> - Phone is then prompted to accept voice commands to dial number.
>
> Has anyone succeeded in or know if it is possible to get totally
> handsfree operated voice dialling via a Bluetooth headset (or any other
> form of handsfree kit) and this model of phone. The instructions
> suggest that it should be possible. It would be a great help as she
> has already gained a great amount of independence from using auto
> answer functionality so completely hands off dialling would be the
> icing on the cake.
>
> Many thanks,
>
> Tom