I'd gladly pay a dollar for a "Passcode Lock now!" iphone App.
The iPhone provides Passcode auto-lock. That's fine, but it's dangerous to enter a passcode while driving. So I set the interval pretty long -- to about an hour.
An hour is fairly long. I'd like the option to passcode lock the iPhone on demand. Tapping on an app would be just the thing.
Of course I've no idea whether the API allows software activation of the Passcode lock. I can imagine that might be abused ...