For added security, Burner's app for both iOS and Android comes with a PIN Lock feature, with optional TouchID integration.
Activating PIN Lock for Burner
To activate PIN Lock, tap the lock icon in the top right-hand corner of the Inbox.
You'll be presented with this two-step lock workflow. Tap "Lock" to proceed.
Enter a 4-digit PIN (personal identification number) that you will be likely to remember. You'll be asked to enter it twice to confirm.
Then press "Lock" when you're done.
On the next screen, you can enable TouchID on iOS if you want to. If you're not sure how to enable it on your Apple device, visit Apple's support center article on TouchID.
Deactivating PIN Lock
To disable the PIN Lock, tap the lock icon in the top right-hand corner of the Inbox.
You have the choice of a temporary unlock, or to unlock the app completely.