So you're throwing a party and you're rocking a Google Chromecast as the source of all entertainment when a sketchy friend of a friend says he has an awesome playlist or video he wants to share with the crowd. "Dude, like, what's your WiFi password so I can share, eh?" he asks.
What an awkward social position. You really don't want to give this individual your password because he's wearing a 'defcon.org' t-shirt and he has on those fingerless gloves that all hackers wear. (I know this is what hackers wear because I watch a lot of TV.) Everyone is looking at you expectantly. What do you do?
There's no right answer and from now on there doesn't have to be, because Google has unleashed "Guest Mode" on the world. Guest Mode lets anyone using an Android device sling things to your Chromecast without being on your WiFi network. (Just make sure not to invite any iPhone or Windows Phone users to your parties.)
What's really neat about this is how it works. Google says your Chromecast generates a random 4 digit pin and broadcasts it using "short, inaudible audio tones" that the potential casting device can hear in order to pair up. The guest can also just punch in the PIN (it'll be displayed on the Chromecast's homescreen as well) if the automagical pairing fails, but that's not nearly as cool.
I put it to the test by turning off WiFi on my Android phone and...it didn't work. That's because WiFi has to be on, the device just doesn't have to be connected to your network. What you're doing (I'm assuming) is pairing the device with the Chromecast itself, without involving the local WiFi network. So for my second attempt I "forgot" my home WiFi network on my phone, but left WiFi on.
I fired up YouTube on the phone and the Chromecast icon showed up. When I tapped the icon I saw my Chromecast listed as a "Nearby Chromecast." Tapped on that and got a popup telling me my microphone would be used to connect to the Chromecast. Once that had happened it was pretty much business as usual for casting content.
Guest Mode isn't on by default; you can turn it on from a Chromecast app. It's the top option on the Device Info screen that you get to by tapping on your Chromecast in the app. It's probably not something you want to leave on all the time since it does allow anyone in range to connect to your Chromecast and your Chromecast is connected to your network. I'm no security expert but that seems like something that could be taken advantage of given enough time. The good news is it's super easy to turn on when you need it, and turn back off when you don't.
Another nice feature for the Chromecast. Thanks Google.