Last week I mentioned a nice straightforward guide on the basics of implementing touch ID authentication in an app.
Here’s a library allowing you to easily use Touch ID to for app authentication called EHFAuthenticator from Christopher Truman of eHarmony.
EHFAuthenticator allows you to present the user with a view asking for authentication via TouchID, and executed a callback on successful entry.
This set of images from the readme shows a mockup of the feature in the eHarmony app:
You can find EHFAuthenticator on Github here.
You can read more about Touch ID authentication over on Christopher Truman’s blog.
A nice library and example on using the touch ID local authentication feature of iOS 8.