Kanex XD

Owners of Apple's 27-inch iMac get an added benefit to the pricey all-in-one's large screen: the ability to send a video signal into the display. This opens up lots of possibilities for connecting game consoles, or a Blu-ray player, and turning your iMac into a true home entertainment hub (albeit, one limited to 720p output due to the iMac's display settings).

You'll need an adapter here as well, but in this case it calls for something a bit more heavy duty than a simple dongle. Instead, you'll need a product like the Kanex XD, which was specifically designed to send video into Apple's largest iMac.