I want to create a device which is not only controllable by voice but also programmable.
Would probably start with something like the MT2502/rephone/linkit one. The device would include a speaker and microphone as well as bluetooth or headset jack for getting sound in and out.
For software I would try to pare down a voice synth such as espeak or maybe get real crazy and use something like SAM (Software Activated Mouth).
For voice recognition I would try to port pocketsphinx or if I had to use a cloud service.
Normal siri/alexa/google now voice control of course would be available but there would also be a programming/debugging option where the device could read code or mention interesting log events and you could talk the computer through changing code, testing, reverting changes, etc...
As a special challenge maybe there would be a machine language mode in which you could enter machine language codes with a series of clapping or other primitive noises... kind of like morse code dot dot dash dash might be 0 0 1 1 which might be a branch 0 instruction aka infinite loop.
The idea is to make something that is everyday useful as most objects are but then also nearly infinitely explorable and modifyable as an object itself.