I'm not sure if this exists yet but I'd be willing to pay $2, even $5, for it. Although the lock screen is useful for keeping unauthorized people out, sometimes a friend wants to check Facebook, look something up, or just play a game but they have a dumb phone. There needs to be an app where you can lock certain apps [such as the market (just in case they accidentally buy something), gmail/email (for obvious reasons), or maybe that app that you use when you're lonely and bored (lolz!)]. To enter the app, you could either either a number code or do a pattern like on the lock screen. Apps should also require a password when accessed from the notification bar. However, if you're sick of it always asking for your password/pattern, there should be a way to turn it off (like when you're using it and nobody wants to use your phone anymore). There's an app for this on a jailbroken iPod/iPhone in Cydia called Lockdown (I have it on my 1st gen iPod). Feedback?