You must use Safari Mobile in order to add a shortcut in your home screen.
iCustom has been entirely made for Apple iOS devices (iPhone, iPad, iPad mini, iPod Touch, ...).
Because of the lack of customization possibilities on iOS devices (currently iOS 7). And because I own an iPhone and an iPad !
This means that all the terms and procedures used in this webapp are iOS related.
However, iCustom should work on Android and smartphones with other mobile operating systems.
If these systems can launch applications using URL schemes and if they can add icons shortcuts to web pages, it might work...
I didn't test iCustom on other systems than iOS, and I cannot give any garantee !
iCustom is « just a website », so of course you don't need to jailbreak your iPhone or iPad !
It uses iOS and Safari mobile core functionnalities as a workaround to launch apps with home screen shortcuts.
This also means that we can't do anything we want, and there are many limitations.
We can launch with iCustom only apps that can be launched with an « URL scheme », and you won't have on these shortcut icons the notifications.
A jailbroken device can do many more customization things...
Again : iCustom is « just a website », not a native iOS application.
All you have to do is to visit it from Safari mobile.
It is important to use Safari mobile on iOS devices because only Safari can add shortcuts to websites on the home screen.
Once added to your home screen, you can launch your apps even if you're offline (not connected to internet, in airplane mode for example).
You'll just have an iOS message telling you that you are offline the first time, but your app will launch.
Of course, you need to be online in order to configure an app shortcut and add it to your home screen !
A great iCustom feature is that you can configure some websites shortcuts using the browser you want when launched, instead of the default mandatory iOS Safari mobile browser.
Just go to the configuration page and choose the « Web browsers » application type item to choose the browser.
Then set the URL address of the website you want to launch with the selected browser, choose your custom icon and you will add the generated iCustom shortcut on your home screen.