Good for swallowing up if something goes wrong (let's say, at a border crossing) or for places where the stuff hiding is a primary concern (let's say for those who are jailed).
Unless this hardware wallet ring becomes immediately conspicuous for anyone looking at it longer than a second, I wouldn't worry about it. People own various pieces of jewelry that they wear and cross international borders with all the time without any problems. If you get jailed, you'll have your valuables, such as jewelry taken from you by the officers, to be returned upon your release.I shouldn't be surprised if something similar and designed exclusively for rectal use would appear. 
There is an interesting business model. Perhaps a hardware wallet worn on your manhood or a vibrating one for the kinky crypto enthusiasts.