Cycling hydration system replaces a cage with a pin
The traditional bicycle water bottle cage is one of those things that some people are just determined to make obsolete. Over the years, we've seen alternatives like studs and magnets put forward. One of the latest such inventions, the Freedom Cycle Hydration System, uses a bike-mounted "pin" that plugs into a hollow section in the bottom of the bottle.
On smooth roads, the bottle can just be pushed on part-way, so that an O-ring on the front of the pin engages the hollow in the bottle (users can in turn choose between different O-rings, for different amounts of tension). For rougher roads or off-road trails, the bottle can be pushed on all the way, so that a larger molded ring on the pin also holds the bottle secure.
So, what's the point?
Well, among other things, the Australian-designed system is claimed to be easier to use than a traditional bottle cage, more aerodynamic, plus it won't scratch up the sides of the bottle. It does require the use of system-specific bottles, though, so you can't just grab one at your local bike store.
If you're interested in getting a Freedom Cycle system of your own, it's currently the subject of a Kickstarter campaign. A pledge of AUD$25 (about US$20) will get you a pin and bottle package, when and if they reach production.
It can be seen in use, in the following video.