The Trenscend uses a in hose absorbent "sponge" which trapped the heat and humidity from the exhale and transfer it to the inflow air on the inhale. This is what they claim. I will report how well it works after some usage.
http://www.mytranscend.com/
I find I need some type of moisturizing. When I travel without the humidifier unit I depend on saline nasal spray and water based nasal gel.
I intend to use this for travel and the Resmed 9 plus humidifier for the two "homes".