Adorama via eBay Daily Deals offers the GoPro HERO4 Black 4K Action Camera for $399 shipped. That’s $101 off the regular price/Amazon, a match of our previous mention and the lowest current listing we can find.
The GoPro HERO4 Black can record 4K video at 30fps, 1080p at 120fps and capture 12MP still photos. It is waterproof up to 131 feet with the included housing. Built-in Wi-Fi and Bluetooth enable this camera to wireless share photos and videos.