Space-efficient they're not, but is there a cyclist alive who wouldn't prefer storing their bike in a locker rather than shackling it to a signpost?
Velo-Safe is a bike locker system produced by UK-based Cycle Works Ltd and reportedly sells them in Europe and the 'States, though I've never spied one. Although I love the idea, I feel the design is simply too bulky to see mass uptake; there are limited situations where you can find dead space to tuck them under, as with the stairwell below, but those types of architectural dead spots are few and far between in crowded cities, which is where these lockers are needed most.
One city that could really use these is Core77's hometown of NYC, where you can find a signpost-shackled bike that's been picked clean of parts on seemingly every other block. But even if we could fit these lockers in our city, it would only be a matter of time before our homeless started living in them. We've got problems, folks.