Kosta Peric knows better than most how banks can provide innovative services for the poor.

Peric, who is deputy director of financial services for the poor at the Bill & Melinda Gates Foundation and former director of communications for Innotribe, spoke with JJ Hornblass at Bank Innovation 2014 in Seattle earlier this month about more than just servicing the poor. In the wide-ranging conversation, Peric described his concept of the “the castle and the sandbox” — also the title of Peric’s book — and gave the example of bKash, a bank-funded money movement service for the underbanked in Bangladesh.

Peric said that serving the poor, far from being a financial drain on banks, can yield unexpected value. Hear more below.