What he's looking to do is to be able to remotely control the mouse without the knowledge of the user, ostensibly to send commands/macros to obtain remote access without the user's knowledge, or capture movements to determine what the user is doing. This is similar to hardware keyboard "bug", which can intercept as well as spoof keystrokes. These have been made before in varying degrees of complexity with varying degrees of success since the 70's. In our case, he's asking us to help him with mouse/keyboard emulation.. though he claims he's already implemented some kind of remote access IP stack, which is exponentially more difficult than simply reading the documentation for an Arduino lib. If he's written an IP stack, then he needs no help with an Arduino lib.. so we're dealing with someone else's code on top of everything else, aren't we? It's not "your code", making this even more suspect. Methinks there's a LOT more to this particular little request, and I'd advise both he and anyone considering assisting him that this is not something you should be doing, much less asking for help to do it on a public BBS. That makes it obvious you aren't a professional or someone that ought to have a device like this in their hands.
Really- dude, stop before you get yourself in real trouble. It's obvious you are in WAY over your head. I applaud the curiosity, but this isn't something to play with. Just take me at my word on that... it's not a particularly bright time (as if any time were good) to advertise that you are attempting to develop a novel way of breaching IT security. Doing it like this makes it clear you don't understand the ramifications of what you are asking for, or the fact that you could go to jail just for trying.
What you are asking for is assistance with a project which violates pretty much every privacy law in any country, as well as a wide selection of international laws. I'd suggest that since he's trying to do something with no other purpose than to illegally obtain access and information, he's a total fool for asking for help to do it in PUBLIC FORUM..
You are aware of this, aren't you? Bugging devices are something that some folks take very seriously.. ranging from McAfee to the NSA.. and building something like this or owning it is a FELONY in many places. Using it.. that's a guaranteed trip to jail if it's prosecuted.
Don't be surprised if you get some people really interested in WHY you want this, and your plans once it is made...You aren't by chance on Rupert Murdoch's payroll, are you?