Three words...
Rhodium Keyboard Controller. You can map any key by single, double, or triple click or long press. It has actions to toggle wifi and BT that can be assigned to such a key. I don't toggle BT because I leave it on all of the time, but I have my long-press HOME key mapped to toggle wifi. Works like a charm.
Take a look at this thread to see what others are mapping using this app...
Post your Keyboard Config