[matthewmacleod]

Voice recognition is 'on' all the time as it needs to recognise 'keyword'

Not to say it's not a concern, but that's not really how these devices work – at least in the Alexa case. They're just matching for a specific hotword, rather than constantly performing speech-to-text (which is computationally expensive and done remotely). Think of it more like Shazam or the other audio fingerprinting services – you don't have to actually transcribe the text to understand if a particular word has been heard.