If you have a smartphone made in the last 12 months you are very likely to have voice command capability. In the mid-1980s the improbability of talking to your computer was shown on the movie Star Trek IV – The Voyage Home. Mr Scott was trying to use computer to create transparent aluminium but found that the Apple Mac (brand new at the time) was unable to understand voice commands.
Star Trek was set in the world of the late 23rd century so when you find Siri, Google Voice Search and Cortana on your mobile device the real world is becoming stranger than science fiction.
My first experience of mobile voice devices was being driven home one evening from work. On this particular contract I took public transport but tonight I was offered a ride. My colleague had a new(ish) Apple iphone and during the journey he decided to text his wife while driving. Voice commands with Siri supported this. Unfortunately he was from India and had developed, through his work in the UK, a northern British accent. The result was a complete inability of Siri to pick up even the simplest words accurately. He had more success with the weather as the iphone declared that the weather would be fine. Since we were driving in a rainstorm that proved somewhat optimistic.
Google Voice Search seems pretty good. I have used that a few times on my Android Nexus 7 tablet. It is an accurate way of doing search and does not overstate its usefulness. When combined with Google Now it can tell you quite a lot but it does depend on disregarding your privacy and being a bit creepy. I don't take the tablet out and about too often but on a couple of occasions it noticed I was in the same place and thought, as it was away from the house, it must be work. It was wrong and started reminding me I was late for work. Accuracy depends on understanding your life but it provokes the question of whether you want Google to understand your life that much.
Then there is my phone – the Lumia 1020. Microsoft claims that my voice search called Cortana is a digital personal assistant. It's not quite as creepy as Google because you can keep stuff on the phone and out of the cloud. Cortana promises it will use personal preferences without recording them. I have found that it copes with my British accent pretty well but it seems to still have difficulty discovering where I work, helping me with public transport and the personal information that you would expect a personal assistant to know.
We are still some way from Star Trek but I am amazed we are this far along at all.