Bluetooth was another feature that was lacking in Windows Phone 7.X. In Windows Phone 8 will be able to access the Bluetooth stack via API’s and will be able to communicate with other devices. These same API’s also allow the ability to connect to 3rd party peripherals.
Windows Phone 8 phones will also be able to find other Windows Phone 8 devices in close proximity and share media and information with them, akin to the Zune’s”squirting” functionality from a long time ago. I’m sure more about Bluetooth functionality will be revealed in the coming months.