Today I managed to get audio warnings of traffic cameras, without loading the POIs into the navigation system (which I can't do anyway, as I have the Discover Nav and not Nav Pro)
This method could probably be used in conjunction with the visual display of the POIs as detailed above - perhaps someone with Nav Pro could confirm?
The method I used is as follows:-
I have an iPhone 4S which is paired via bluetooth to the car.
On the phone is the Pocketgpsworld Cameralert app which uses their database.
In the settings for the Cameralert app, the audio route is set to bluetooth.
With the app running, when you approach a traffic camera the app routes the audio warning message via BT to the stereo, interrupting any music playing/radio etc. After the warning, the music resumes.
I confirmed that this method worked tonight while playing music off the SD card, and whilst there is no display on the nav screen, there could be with POIs loaded into the Nav Pro. I think it should also work on the CMS stereo, as it is just bluetooth audio that is being used for the warnings.
There are a couple of possible disadvantages to this method of warnings.
1. The app does tend to drain the phone battery more than normal, as the GPS is running all the time - therefore it might be better if the phone was plugged in to charge. I've yet to test whether enough of a GPS signal can be received if the phone is hidden away and plugged into the iPod lead.
2. I'm not sure what would happen if a phone call was received, and which audio would take precedence.
I presume the Android version of the Cameralert app would work in a similar way, although I can't check this either.
Hopefully this will be useful to some of you.