Cloaky allows you to add date/time/RAM/IP and all the good stuff, but it does run you a buck and a half, but it also allows you to hide some features as well, so it's a plus. The developer did say that he was planning on including the IP string, but that was back in January and I don't see the option in StatusModifier as of now as well, nor is it in the Change Logs so I'm guess he never got around to it. You could message the developer about it possibly.
EDIT: yBox also does the same thing, but it runs you twice that of Cloaky. However, it's limited to only 2 strings AFAIK, so if you want Date, Time, RAM and IP all at once, you'd have to compromise with the top 2 that you prioritize i.e. Time and IP only, or Time and Date only. Cloaky's only limit is the availability of space on your statusBar (more stuff going on in your statusbar, less room you have), but if you're on an iPad, then you have all the room in the world.