Picture this: you're in a coffee shop, surrounded by strange people and you need to use the restroom or run to your car, what do you do? Do you trust anyone to watch your stuff? Do you go hoping to come back before Mr. Sticky-fingers arrives? No, now you can watch your own stuff (and feel like a spy) by using FaceTime to see exactly what your computer sees.
First off, you will need a MacBook, MBPro, or MBAir and iPhone 4. FaceTime comes stock on iPhone 4 (under the phone app) and FaceTime for Mac is available on the Mac App Store. When you open the Mac app set your email to whatever Apple ID you choose and make sure that email is under your contact information in your iPhone. Also, FaceTime requires that your iPhone be on WiFi not 3G., since you're at a coffee shop this shouldn't be a problem. Launch the 'phone app' on your iPhone, open your contact info, and click FaceTime at the bottom. When you click FaceTime, select the email address (Apple ID) you chose to use in FaceTime on your Mac. Wait a few seconds and it should send a video chat to your computer. If everything worked properly you should see what your computer sees. Immediately click Mute on your iPhone and Mac to avoid the incredibly annoying feedback loop.
There are also a few side comments I must make. I didn't really want people passing my computer to see the chat window (since on the other end would be me in the bathroom) so during the call I attempted to send my MacBook Pro into screensaver mode, which would work for a few seconds, but the screensaver would automatically turn off. I went into system prefs > security and set the 'password to unlock from screensaver/sleep' function. This worked great. The screen was black with a login window and the call was still going in the background. On first attempt the call ended after a few minutes, not sure why, but it did work for a while.