Well I've not seen anyone else actually use one so thought I'd post my first impressions.
I purchased a Coros bike helmet at the Noosa Expo the other week (a white one with the red highlights) $229 at the exp - discounted from $249 RRP (but equal to the going rate on the interweb)- bonus t-shirt at the expo though.... The price seems pretty good and cheaper than a premium quality helmet ( which it seems to be) plus a pair of Bluetooth headphones.
This helmet uses Bluetooth to link to your smartphone and has bone conduction pads fixed to the straps so that they contact your cheekbone