From the publisher:
The Dept. 7 Technology Update line gives D20 Modern players and Gamemasters a detailed look at a specific cutting-edge technology for use in your game. Use them as plot hooks or as the bleeding-edge tech issued to Dept. 7 Agents.
Liquid armor is the most flexible, adaptable form of protection available to Dept. 7 agents. It's strong enough to resist small arms fire, and no bulkier than clothing made from ballistic fabric. As the armor technology developed, steel and ceramic ballistic plates were replaced by a liquid component that would harden when needed into a "temporary" plate, and then return to liquid state. Advanced versions of this tech incorperate nano-enhancements to create armor that adjusts to the specific threat, and react accordingly. This tech has found use in personal armor, vehicles and even shelters.
This PDF covers a history of the Liquid Armor technology from its inception and development through several progress levels of advancement.