I don't think Square counts as a hardware startup.
Food for thought, is a bank that only provides internet banking services and providing a 2-factor auth dongle a hardware company?
In fairness, I doubt most traditional banks actually design their own 2-factor authentication hardware. But yeah, calling Square a hardware company is nevertheless a stretch. (particularly as the hardware component is a freebie/loss-leader IIRC)
All of these companies are great, but have any of these companies reached sustainability? Most seem like they are still in investment stage and are trying to grow the company. I guess Square is the only exception here because they have a secondary revenue which is transactional payments.