If you are an iPad or iPhone 3 or 4 user who is about to loose Siri since it will now only work with the new iPhone 4S, an Android, BlackBerry or Nokia user you can try Vlingo. Vlingo is a virtual assistant app like Siri.
The app is free on Android, though add supported. It costs US$1.99 to remove the adds. On the iPhone and iPad, it is free but you have to pay US$6.99 to enable it to be used with email or SMS. It costs all of US$9.99 for use on Nokia. It is a whopping US$19.99 for the BlackBerry.
I am not much for virtual assistant, but I have tried Vlingo, and it does work. It is a much better at voice commands than the built-in to the default Android voice commands. It has a useful hands free in care mode and an SafeReader which reads your incoming SMS and email. I have it installed, but I really don't use it. I guess I just don't like talking to the phone. Another reason is battery life, with all the things going on with my phone (it automatically updates email, calendar, contacts, news, twitter, news and weather and a instant messenger on 24/7), it just is not a priority for me.
It is mostly free for Android and iOS. Give it a try or watch it in action: