IIRC the original innovations of Simple were (1) usable UI (including mobile) and (2) a single account that's debit and credit. #1 has been mostly caught up by traditional banks and #2 mostly benefits financially irresponsible people (of which there are many, but perhaps not many around here).
Their original claim from 2010 was "We will launch later this year with a simple card with in built checking, savings, rewards and a line of credit." Since they're still in invite-only beta, maybe not all of the features have been implemented yet.
