Hmm... it certainly works for me. Granted, I haven't sorted out any bugs such as seekers/arrows or whatever had been mentioned; just making sure the basic code works first. But patching the server with this code definitely makes the client see nothing outside his screen (client doesn't need to be patched), and a health of 7. I should probably add some notes here: firstly that the player doesn't "disappear", he simply stops moving once outside the visible region. and secondly that the health is shown as 7 only when player enters the visible region, and is not updated otherwise. (doesn't have to be 7. anything from 1-7 works by changing the middle byte)

Of course, I only tested this on v1.23 (not plus), in both battle and ctf, so it might be some plus implementation. I don't have this Radar app, but however it works it can't possibly obtain information which isn't being given.