Bloch created Digit, an app that automatically saves money from your checking account without your even having to think about it. He got $2.5 million in seed funding from Baseline Ventures, Google Ventures, and a handful of other firms last December, and the app opens to the public Thursday.

The way it works is simple. Once you connect your checking account to Digit, it will automatically transfer a small portion of your money that it knows you won’t be needing immediately to a separate Digit savings account. These are FDIC-insured, custodial accounts held by Digit at two of its partner banks, Wells Fargo and BofI Federal Bank, meaning that even if Digit or both those banks go bankrupt, you will be insured up to $250,000.

The secret sauce is in Digit’s algorithm, which monitors your income and spending patterns and calculates the exact amount of money you won’t be missing.

But your Digit savings earn no interest?

Correct, that's Digit's business model. They keep the interest on dollars you save through them.

It is an app for people too spendy or too lazy to save money themselves.

On the other hand, it's not like interest rates in savings accounts are anything special right now anyway.