I think you would need the motorcycle version to have instructions via bluetooth.
I have just bought myself a new TomTom (I now have two) and I hope I can find somewhere to fit it, so this thread is quite interesting to me.
I find that I use the visual instructions quite a lot so I hope to find somewhere to fit it where it can be seen. If necessary I will construct a visor to shade the screen. In my Alfa I have always fitted the navigator to the drivers side of centre of the windscreen but as low as possible.
If that blocks the view too much perhaps the driver's side bottom corner?