I've made a proof of concept of a voice controlled UAV using a Parrot Bebop 2. Voice recognition is done in a Raspberry Pi 3 thanks to Snips.ai it is done offline, you do not need internet.
Here is a small demo :
As you can see there is about 3 second between order and action, so don't fly near obstacles !
Maybe it could help disable people to fly UAV and experiment FPV. If you find it useful let me know.
A largest use case for vocal assistant in UAV could be to talk to Mission Planner to query information about battery or altitude.
More details on my github.