I think this is possible. When you launch a game (steam or non-steam) Steam detects the game and launches a process I think is called SteamOverlay.exe. I believe that process injects a .dll file into whatever game you are playing and that shows the overlay ingame. Then, the .dll file updates your chat, friends list etc. through the process. I've gotten this information by playing BF2142. Everytime I joined a server with steam ingame enabled, I've been kicked in 10 minutes or less and I get this error that says PunkBuster doesn't recognise a .dll so then it kicked me. I can't remember which .dll it said though and I am to lazy to reproduce the problem. However, if PunkBuster doesn't scan steam, which some guy said up there, and we found that .dll file, maybe we could replace it with a hack and steam won't detect the change. Then Steam is tricked into injecting a hack into APB. This is my understanding of how steam ingame works.