Strong password? Of course NOT. The best proector would let prier not be aware of any protection. App Locker II is one such protector to protect your private apps.
★ How it works?
When launching a protected app, it will throw a fake crash error which may mislead guest user into thinking that your app has a glitch or something. So it can stop guest from using your protected app in a natural manner.
For owner, it provides several secret unlock methods to unlock it without a trace. Of course, it also provides a password protection with a secret input method.