[pat2man]

This is not the proper solution. Instead of making your data accessible when the device is locked you should listen for UIApplicationProtectedDataWillBecomeUnavailable and UIApplicationProtectedDataDidBecomeAvailable. Once your keychain item becomes available again you can log the user back in. The keychain will always be available in the foreground.

[lnanek2]

Sounds like a much better solution than many of the other proposals here, which would end up with the user having to enter their login credentials more often than they'd like.