Bluetooth disable WiFi

Dislaimer: You really might want to use a Bluetooth USB dongle. The internal Bluetooth module of the Raspberry Pi (all versions) is very limited and using it for audio transmission will most certainly lead to problems and unexpected behaviour, see raspberrypi/linux/#1402.

If you really want to use the internal Bluetooth module, you almost certainly need to disable Wi-Fi.

Modify /usr/local/bin/bluetooth-udev and remove the comments (#) around the ifconfig calls:

...
if [ "$action" = "add" ]; then
    ...
    # disconnect wifi to prevent dropouts
    ifconfig wlan0 down &
fi

if [ "$action" = "remove" ]; then
    # reenable wifi
    ifconfig wlan0 up &
    ...
fi