Pony up for T-Mobile.
As suggested, if you have to, spend $10 every 3 months to keep it active (or more if you run out of time, of course). Once you've hit $100, your next topup will extend expiry by a year (if you put in $100 immediately at the beginning, you get a year of validity instantly). Also, it roams at the same rate within the US, so even in areas without native T-Mobile coverage it's quite usable.
CA: SaskTel, Wind postpaid; Rogers, Bell postpaid iPad flex plans; US: T-Mobile postpaid data, prepaid voice; PureTalk (AT&T MVNO) prepaid voice/data; AT&T prepaid iPad plan
Hardware: Too much but notably iPhone 5, iPad Mini Retina LTE, Moto G LTE (N.A. version), iPhone 4. All unlocked.