An version of Nvidia's GeForce Experience software will allow players to stream co-op games to a friend's PC, even when just one player owns the game.
Called GameStream Co-op, the software is able to stream your videocard's output to a friend's PC at 720p and 60fps, meaning a buddy can either watch you play or even take control of the game themselves.
In shared-screen (think Magicka 2) or split-screen (think Borderlands 2) co-op games, both players can take control of the same game, even in cases where just one player owns it. Thank you, clever internet magic.
The updated GeForce Experience will also allow s to record gameplay footage in the background, allowing you to save the last five to twenty minutes to a gallery at any time with little impact on performance. The new overlay features YouTube integration for ing clips, as well as Twitch integration for straightforward broadcasting.
The new features are available to anyone running a GTX 650 or better, and will require a chunky old bit of internet piping to properly work: a 6Mbps for the streaming player is recommended by Nvidia.
Nvidia are running an Early Access beta of the new features ahead of their full release. You can find out more over on their website.