SiliconBeat writes about a US-based service:
Here’s how it works: Pinger gives you a local number that you store in your phone under “speed dial.” Whenever you want to use the service, you press “p”, and it dials a local number. So far, you have just pressed one button.
Pinger then gives you a prompt, and then you simply say the name of the person you want to call (your phone must have the person’s contact details stored, such as email address and/or phone number). Pinger uses voice recognition (from Tellme) to look up their details. Pinger then gives you a second prompt, and you speak your message into the phone. Pinger then sends the audio message to the person’s email account, or to their phone via an SMS audio file. So the person on the other end can listen to it immediately or later — but the main point is, you’re not locked into actually talking with them.