Groupon offers the factory-refurbished Google Chromecast Streaming Media Player for $18. Better yet, add two to your cart and apply coupon code "VISA5" to cut the price of both to $35.10 with free shipping. That's $17.55 per unit and the lowest total per-unit price we've seen. It's also $21 under what you'd pay for two new units. It attaches to your HDTV's HDMI port and connects to your wireless network to receive streaming online video, music, websites, and more from your smartphone, tablet, or laptop. A 90-day Google warranty applies. Deal ends September 13.