Hydration Technologies’ SeaPack Emergency Desalinator does not use the reverse-osmosis process we’re familiar with to remove salt from seawater. 
Instead, it uses conventional "forward osmosis", where water moves across a semi-permeable membrane without any pumping in order to equalize the "osmotic pressures" on either side of the membrane.
The end result is that the SeaPack produces a potentially life-saving drink directly from seawater. The filtered drink is said to be similar to grape juice, providing 480 calories from each half liter. The osmotic membrane rejects 97% of the salt.
If you don’t own a portable reverse-osmosis watermaker, this is a compact, lightweight alternative for your emergency kit. MSRP is $99 for a single SeaPack filter and five "sports drink" syrup charges.
They even sell them through Amazon.com
