I'm BankSimple's CTO. To your points:
1. We're more than a "customer service wrapper". We don't license our technology or outsource our support staff to other banks. Banks are our partners, not our customers, and we only partner with a small number of banks who share our values and are willing to set aside things like fee revenue to work with us. We have a symbiotic relationship with those banking partners: we bring them deposits, and they make loans on those deposits and share the resulting interest margin with us. That is one of several sources of revenue for us, but not our sole source of revenue.
2. If customers like the way we help manage their money, we're able to connect them to a variety of financial products that are mutually beneficial to our customers, our banking partners, and to us. As above, our banking partners are happy because we're bringing them new customers for various financial products, many of which have a decent margin on them (CDs, for example). We share that margin with our partners, and that's another source of revenue.
Our business is all about aligning the interests of the banking industry with the interests of our customers. Where we can create that alignment, we profit.