Canadians, I know you think Roam Mobility is a good deal... I would too if I wasn't familiar with the US options and the only prepaid mobile pricing I knew was the pricing structures of Canadian MVNOs like SpeakOut, Petro Canada, etc. Well, it's not, especially for a T-Mobile based MVNO - which is going to giver far spottier reception in Hawaii. If Hamildub wants to go with a T-Mobile MVNO, P'tel would be far cheaper, even with the extra penny charge for Canadian calling on their PAYGO plans.
I'll readily admit, I spaced a bit on the whole calling/texting Canada bit, but H2O has the best PAYGO rates to Canada, and H2O and Airvoice both include international calling credits on their unlimited plans. No matter who you go with and how long you're in the states, there's no sane reason why you should need to spend more than $30 for the entire stay for up to a month of service, just like the rest of us, and you could probably get out for a lot cheaper.
Speaking of T-Mobile MVNOs, Hamildub? Do yourself a favor and keep a healthy distance between you and SIMple Mobile, no matter how tempting the offer on the surface.