Vincero Designs' Edge16 system comprises both a slim magnetic mount and a purpose-built water bottle with a magnet built in it. The two magnets lock together, providing a powerful bond to keep the bottle securely on your bike. The main advantage is the beyond-tiny weight of 16 grams.
Another advantage that the design might offer is that it seems like it'd be easier to pull your bottle straight off mid-ride than to have to finesse it in and out of a cage.
Source: inventorspot.comAdded: 20 October 2011