My Android phone connects to my Yeti's BT module quite happily each time I drive it. That's great for the actual phone functions, but it seems that the only way to get the BT Audio option on the Bolero to light up is to actually stream music from the phone. That's not ideal if the only audio source I want to use is a Sat Nav application on the phone, and to have the voice directions come via the car speakers.

Is there a way to get the Bolero to recognise that the phone wants to use BT Audio, without streaming music from the phone?

No

The Columbus is the same.

But thinking about it, can't you set up playing music from within the sat nav app? I know the iPhone can. Then turn the volume down to zero, but still have the voice directions come through the speakers?

I think that depends on the Sat Nav app. Google Navigate on Android doesn't seem to offer the option.

Mind you, when I tried Google Navigate on my normal run home last night it tried to get me to turn right at a no right turn junction, then rerouted via some horrible right-hand turns and an utterly unnecessary traffic-calmed street. I've tried a couple of "free" Sat Nav apps from Google Play (which, for some completely farcical reason, is the new name for the Android Market): one didn't actually navigate at all, the other tried a similar trick to Google Navigate in trying to get me to do an illegal manoeuvre and was thus swiftly consigned to the bit bucket.

I suspect a standalone Sat Nav may be the better option. They seem to be pretty cheap these days.