But up here in San Francisco, I saw a row of bike racks in the Financial District which actually seem inspired by parking meters! So of course I took a photo:
While these can hold only one bike each, they still work quite nicely, and...perhaps the design could be modified to convert disused parking meters to bike racks on streets where paystations have been set up.
It might provide a simpler, cheaper way to provide bike parking in cash-poor US cities than the slipover rings I've seen used so far. The rings are superior, as they can park two bikes each, but if these knobs are cheaper we might see more of them.
It's good to have options. And a lot of inverted-U racks--the most often recommended type--can't really fit two bikes anyway...at least not two bikes that have racks, basket, or pannier (or all of the above).
Even San Francisco, which I'm bicycling in this week for the first time, doesn't have enough bicycle parking. Every little bit extra will help a lot.
Bike lanes don't matter much if you can't park your bike safely when you get where you're going.