Emdebian is essentially Debian but a binary distribution for embedded hardware where limited RAM and disk space are critical. Embdebian works with regular Debian tools but effectively re-works upstream Debian so that the packages are smaller by taking greater control over package dependencies, included files/content, and other tweaks.
Emdebian Grip is their smaller distribution in binary form that's ready to go while Emdebian Crush is a cross-built version and Emdebian Baked is another variety that allows for placing the distribution in a static configuration. The Emdebian flavors are covered in more detail on this web page.
Emdebian Grip is binary-compatible with Debian while a basic multi-strap of Sid is significantly smaller: 56MB for Emdebian Grip versus 90MB for Debian. Emdebian Grip is about 40% smaller than Debian through its re-packing techniques, etc. Emdebian Grip releases are also done along side the upstream Debian releases.
At DebConf this week in Managua, these were the basic details covered about Emdebian, with nothing too terribly exciting come out unless this is your first time hearing of this embedded spin of Debian. More information is available at Emdebian.org.