Slightly off topic, but I thought I'd try out voice-only sat nav from my phone using wired in-ear noise-isolating earbuds.
It worked very well - a lovely quiet ride with a gentle voice telling me where to go, and the occasional bong when I went over the speed limit ...
... until I looked over my shoulder, caught the 'play' button and had Meat Loaf singing in my ears at full volume.
Seriously considering something wireless now!