I just discovered an interesting "feature" that appeared when I attempted to connect/dial from the BT headset and the phone was locked (the keys are locked, using latest Sprint ROM).

The headset beeped liked it was trying to was trying to bring up voice dialer. The dialer didn't come up but when I unlocked the phone all system sounds were routed to the headset... Once Voice Dialer is activated again everything goes back to normal (i.e. the speaker on the phone took over).

AD

(using PPC6700 & new Plantronics 510, MS VoiceCommand NOT installed).