This might be a little harsh for what seems like a sincerely useful app and startup, but the problem with the "Yo" startups is that it's just raking leaves (money) to compost them or light it on fire. If the value is in the app, sell the app. If the value is in other people's products and services, then there's no value in it. And if the value is in the "idea" then it's hopeless. If the value is in the fundraising, then we're lost.
What I don't see is why the idea, PiggyBank, couldn't be functional in the first week. Just like I don't see why a company needs $X billion with no imaginable costs or expenses to put that money toward.
Let's say it isn't possible to do mobile-to-mobile payments (which I think it is), or online payments, without owning a bank — then why not release the same app and when you do the chores for your parents or your uncle they put money in a jar? Beyond not making revenue, having users is at least some sort of reward. When you have the revolutionary breakthrough, add that to the app.
And finally, don't leave your job over something you think is a good idea. Make it a reality, and if it takes all of your time and it can support you, then make the jump.
Obviously these aren't things any founder wants to hear, but someone with a greater risk aversion might be able to be as productive with a more realistic focus than the average SV press release.
Edit: Obviously this is a little naïve considering all things, but I'd still like to see the payments possible on a "small business" scale of things.