I've created a directly deployable .deb installer file of my iPhone 3GS and 4 Video Camera Enhancer tweaks for iOS5+ (see THIS and THIS, respectively, for an explanation, quick tutorial and sources). They allow for installing the tweaks without having to have access to a desktop Xcode. I've also made sure the installers themselves set the right write permissions of the configuration file (and its enclosing directory) they modify upon tweaking the video recording parameters. This means installing them has become orders of magnitude easier.
As is also explained in THIS article, installing these kinds of .deb files is very easy. Just transfer the deb file (THIS is for the iPhone 3GS and THIS for the iPhone 4) to your iPhone and start the excellent jailbreak file system tool iFile on it. (The non-registered version will work just fine.) Tap the .deb file from inside iFile and select “Installer” from the context menu.
A 3GS screenshot, with the annotated “Installer” menu item:
An iPhone 4 shot (click for the original-sized image!):
Tap Done in the upper right corner.
After this, all you need to do is respringing your iPhone so that the icon of the just-installed app is shown. You can use the free and highly useful (you may need respringing in a lot of other cases) “Respring” app in Cydia, restart the phone (if you don't mind the longer reboot time) or uninstall / install another app (it can also be an AppStore one) on it.
Feel free to report back, any bugs etc. Note that I'm pretty much unlikely to alter / enhance the 3G S version (the model being that outdated); with the iPhone 4 one, however, you may have more luck.