I have written a lot about Roam Mobility and love the fact I can freely use my smartphone without having to pay huge fees to my canadian carrier.
Roam Mobility just announced that it will have access to the T-Mobile US LTE network as of July 7 2014. T-Mobiles new LTE network cover over most major US metropolitan area and will greatly increase your connectivity speed when in the US.
If you have a Roam Mobility SIM card, you will automatically get registered for the new faster network and be notified via email.
I know Roam Mobility has much bigger ambitions than just US roaming services and I expect them to launch some type of global roaming service in the next 12-24 months. Time will tell but it's great to see a canadian company innovating.