Here's what Voice on the Go is all about. You sign up, choose a local number to connect to them, and assign yourself a 4 digit password. If you live in a smaller town and there isn't a number for Voice on the Go you can call any of the numbers. If you're on a national cell plan there won't be any extra cost.
You then go to the Voice on the Go website and put in your email details, and you can upload a CSV file that contains your contacts. This is much easier if you have an iPhone, so more on that later.
Once you are set up and in the car, you can call Voice on the Go, and an automated attendant will ask for your passcode. You'll then be told if you have any emails or SMS messages. You can listen to them, skip them, delete them, or the really nice feature, you can respond to them. You do it all by voice, with simple and obvious commands.
You dictate your mail, and the Voice on the Go software turns it into text and sends it off to the proper destination. As an added feature, your email gets an audio attachment so the person can listen to what you said.
How accurate is the transcription? Very. I sent about a dozen emails and every word was correct. That was calling from a noisy moving car using the Bluetooth speakerphone. A couple of times, when I was on a rough patch of road and issued a command, the attendant would ask me to repeat something, but the system always got it on the second try.