Button control to voice control

My wife is confined to bed and has limited movement due to MS. Her bed has a four button control that will incline/decline the bed at the head and knees. I would like to allow her to operate the bed with voice commands. She would be able to activate an iPad/iPod with a gesture, or I could setup a Raspberry Pi to take voice commands . I have ample experience with programming and some experience building simple electronic circuits, however I wonder about the best approach to operating the motors? Ideally the existing control would be left intact for caregivers. Any suggestions for how to get started with this? I have done some searching but haven't found anything close yet.
Thanks.
Rich

Here is a simple low cost device that you can work with. They are also providing support for arduino (shield).
You can make something like this..
Arduino + Easy VR----> Motor control pads of the bed (can hack into 'em or can make a motor driver)

Its very simple to built. Cheers!