Virtual-office app Slack is adding one of its most requested features: screen sharing. And more than just simply letting a coworker look at what's on your display, you can grant control so that they can add a few lines of code, or values to a cell in a spread sheet. Everyone will have their own cursor for typing and clicking around, which almost makes it sound like Slack is turning your screen into a Google Doc. All thanks to the magic of the internet. Not into relinquishing full control of your machine? Your call participants can still interact, but they'll be limited to drawing on things. Still, that's pretty cool.