If you have an iPhone 3G on iOS 4 and you are trying to turn on / off iOS 4 features on your phone then zToggle is the right application for that. It allows you to toggle iOS 4 functions like Multitasking and Springboard Wallpapers right away. You don't need to re-jailbreak your device with Redsn0w or PwnageTool.
To download the app, simply open Cydia and search for "zToggle" and install the app.
Latest version (3.0) of zToggle brings full support for iPhone 3G and iPhone 4. Using the app is fairly simple. Just load the app from your Springboard and it will give you the options to enable and disable Multitasking and Wallpaper.
Make sure that BigBoss repository is added in Cydia sources before you search for app.
You may want to go through following posts as well:
- Enable Battery Percentage in iOS 4 on iPhone 3G without Redsn0w
- Enable Multitasking in iOS 4 on iPhone 3G without Redsn0w
- Enable Home Screen Wallpaper in iOS 4 on iPhone 3G without Redsn0w