Locktopus is a new useful app in Cydia, it allows you to protect your iPhone apps from unwanted access with your own password. Locktopus supports all iDevices including iPhone 4, works on new firmwares starting from 3.0 till to iOS 4.0.1.
Sure, you need a jailbroken device to be able to open Cydia and install this app, we already have guides to jailbreak your device, follow our guide posted here to jailbreak any iPhone / iPod Touch and follow our guide posted here to jailbreak any iPad on iOS 3.2.1.
Locktopus is available in Cydia via BigBoss repo for $2.00.
Also, I already covered an app called “Big Brother” [Free] which enables you to protect your Home Screen not your apps with a password and the amazing thing that it takes a picture for the person tries any wrong access.