Cool Siri / Touch ID Combo (UPDATED)
UPDATE: Verge user "roshie" points an even cooler Siri/Touch ID combo in the comments. If you deactivate Siri for when the iPhone 5s is locked, but use a registered fingerprint on the home button with a long press, Siri will activate. But if you try with an unregistered fingerprint, Siri will not open. It is completely seamless, but if you have big fingers like me you may need to retrain your fingerprints for the angle at which you do a long press (it worked for other users in the comments on the first try). I'm going to try disabled Siri and Control Center from lock screen for a month and see how it goes. Only drawback should be Siri access via bluetooth headset is disabled until iPhone is unlocked.
ORIGINAL POST BELOW:
So I stumbled across something cool with Siri and Touch ID.
In the past if I held the home button to activate Siri and said "Launch [App Name]" I would be prompted to enter my passcode first.
However, while I am busy holding the home button to activate Siri, I am also being authenticated by Touch ID and the "launch [app name]" command occurs with no prompt. I expected the iPhone to take me to the passcode screen and await my fingerprint, but Apple combined the two actions.
I confirmed it was not a security breach by trying the same thing by activating Siri with a finger that I had not registered. Sure enough, Siri prompts me for a pass code before launching the app.
Now if only Siri could be deactivated if the fingerprint was not recognized. That would be an awesome feature.