KERV actually started life on Kickstarter - quite a while back - and there's been a few issues moving the project forward. But it's now possible to actually go on-line and order a ring in a variety of colours (white or black exteriors with varying interior colours).
The ring can be used anywhere that a MasterCard contactless card can be used as it behaves a an M/Chip contactless payment device.
The ring is made from a ceramic called Zirconia, so it's pretty tough (the only things that should be able to scratch it are sapphire and diamond) so it should last a while. When using the ring it needs to be held parallel to the reader (not placed on top with your finger flat i.e. bend your finger and the top of the ring should be parallel with the reader).
The website is available to users which allows activating the ring (a unique 'visual' code is distributed with the ring which is then used to activate it on the site). Users can also activate a virtual MasterCard (you get to print out a copy) which can be used for on-line/over the phone purchases. It's actually pre-paid MasterCard so it needs to be topped up. The ring can then be linked to the card too so only one top up is needed for both.Top-ups can be done using another card or by transferring money into the Kerv bank account with a unique reference generated by Kerv.
Being contactless it also means it can be used on the London Underground just by putting your finger near the reader and 'tapping in'.
The ring currently costs £99.99 from the KERV store if you use code ETN10 you'll get a 10% discount until the end of March.
It should be worn as below: -