Mifos Passcode APP
To see its implementation in practice, it's used across the various reference client-facing mobile banking applications maintained by the Mifos Initiative including Mifos Mobile, Mifos Pay Mobile Wallet, and Mifos Mobile CN.
Once a user has fully logged in and authenticated themself into their mobile banking app with their user id and password, they can they set up a 4 digit PIN which is stored locally to quickly log back into their account without re-entering their full credentials. When the user logs out of the app once again, they must re-create their 4 digit PIN.
You can use this to demonstrate the functionality. To download the source code and use in your app visit https://github.com/openMF/mifos-passcode. Contributions are welcome!