In order to install iLocalis on your iPhone you will need to Jailbreak your iPhone in the first place.
Jailbreaking your iPhone will allow you to install third-party apps disapproved from Apple, like iLocalis.
Maybe you are wondering why Apple will reject Apps like iLocalis, well, that is really a mistery, but Apple has a lot of rules and one of them is: Apps can not be running in background.
But of course the iPhone is capable to run this kind of Apps and iLocalis needs to run backgrounded to let you control and locate your iPhone remotely.
So, again, you will need to jailbreak your iPhone to install iLocalis.