Of course the Google Chromecast needs to make this list. The small $35 dongle from Google turns any TV with an HDMI port into a smart TV. Paired with a Nexus 9 you can stream YouTube, Music, HBO GO, Pandora, Netflix and much more from your tablet to any TV and home theater. This is the perfect accessory for any Nexus 9 owner for a wide array of reasons.
$35 from Google Play