The HaZardModding Coop Mod allows you to play the Single-Player Story and all the Secret levels Co-Operatively in Multi-Player. Supporting up to 8 players via LAN or Internet. Each Player can chose one of 3 Classes with specific abilities, to support the Team. Using the Tricorder primary scan mode when close to a Player, will activate the specific Class ability.
In this video the new multiplayer radar feature is explained