The basic idea is that it's a HDMI dongle that supports transmitting web video and other digital content to TVs from other devices, such as your router or smartphone. For example? Sharing photos on a big screen, streaming a movie, etc.
The Streaming Stick, now HDMI port-friendly, was first released back in late 2012, and the Chromecast (pictured below) in mid 2013, but the latter has never made it officially to UK shores (although it is expected soon)...
SVP of product management at Roku, Jim Funk, writes:
This new tiny player plugs discreetly into an HDMI port - perfect for those beautiful wall-mounted TVs - and packs the complete Roku streaming experience. That means access to 1,200+ channels of movies, TV episodes, music, news, sports, kids’ shows and free programming streamed in up to 1080p HD video, plus a TV user interface featuring the beloved Roku Search.
Roku is all about the easiest way to enjoy the best selection of streaming entertainment on TV. That’s why in addition to the included WiFi remote control for the entire household’s use, there are the free Roku apps for Android and iOS devices for those who desire a mobile experience to browse and select content to stream. Users can also cast Netflix, YouTube and personal media from their devices to their TVs and additional mobile features such as the ability to cast content from a computer to the TV are on the way.
In terms of Wi-Fi, it uses 802.11 dual-band (a/b/g/n compatible) with WEP, WPA, and WPA2 support.
It also comes with a simple remote for wider household use, using RF.
The Roku Streaming Stick will cost £49.99 in the UK, from the likes of Amazon and Currys. It is due to ship in April.