In a store in my local downtown area, I saw a sign for AirVoice GSM service that seems to be offering unlimited voice and text. I'm guessing that it's new because of what I found on HowardForums:
HowardForums: Your Mobile Phone Community & Resource - Airvoice Unlimited GSM Official Rate Plans
Also there is a new website:
AirVoiceUnlimited.com :: Unlimited Plans & Features
Is anyone on here familiar with this or other similar companies that use GSM in the US and happen to be have unlimited offers?