There's a sync module and then camera units (the system can cope with 10 units in total i.e. 9 cameras and 1 sync unit). Currently it all works over WiFi, but as there's an Ethernet port on the sync unit, it's expected that it will be enabled with some future version of the firmware.
Set-up is relatively simple, install the iOS (or Android) app, create an account and then it will look for the sync unit (it initially uses its own WiFi), connect to it and select the WiFi network you want it to work with.
It then asks to set-up the cameras, which is done by adding the number printed inside them (you have to open them to put the batteries in anyway), they then get added (and you can name them) and they also connect to the WiFi network.
The camera install is relatively straight forward too, open the back, put in the batteries, push out the bit of plastic in the hole where the mount goes, put it all back together (snaps), put the mount on, then affix the two sided pad and stick it on a wall (or wherever suits).
Though they're battery powered, they should operate for a year under normal operating conditions. The cameras have a motion detection on them (infrared red) and also an LED flash (for night time usage) which is VERY bright. If a burglar were to break in, they'd probably be more put off by being blinded rather than a camera being in the room. The cameras can take a photo or video (720p with audio) and the system can be alarmed and when triggered, your phone will notify you and get a video or photo.
People have used the cameras outside, but they're not waterproof so if that's required, mount them somewhere where they'll be protected from direct rain (like under the eaves or similar).
A single sync module and camera costs $99 (available from Amazon.com or directly from Blink), a 2 camera kit is $159, 3 camera kit $219 and 5 camera kit $399. Additional cameras are $70. Unfortunately they don't seem to be directly available in the UK yet (though Blink will ship to the UK).