A Texas company has released a product called DataJAck that is promising an unlimited amount of 3G data in the USA for $39.95. To top off the offer, they are claiming no activation or termination fees and no contract, you can turn the service on and off as you wish. It would appear they are reselling the T-Mobile AWS band based on their coverage map referencing "AWS 3G Broadband." This conclusion is based on AWS being the type of spectrum (1700mghz) that T-Mobile is deploying here in the USA.
In an earlier incarnation they were promising a 3G VoIP phone as well, under a different domain address, and company name simply listed as "thedatajack.com" which further digging shows the new owners have acquired. Prior to aquiring DataJack, the buyers QUAMTEL were in the business of oil and gas exploration according to a filing.
All of that said, further internet searching raises a reason for some concern, according to Howard Forums.
My hope is this is a good deal and a real deal, for unlimited data in an era where we're going to see price caps and limits becoming more of the norm, makes one skeptical but not disbelieving.