This article describes a proof-of-concept app running on a Nokia 7650 that performs MPEG-4 encoding and decoding, creating a portable video phone. No word on how you can get the code, or how difficult it would be to port this Symbios OS product to other platforms. Still, the company that developed the product, Hantro Products, does supply the codecs that do the trick.

http://www.infosync.no/show.php?id=2016