How can one build a device that presents itself as a mass storage device to a machine via usb, then whatever files are transfered to it, get sent to a remote location via wifi (can be ad hoc). Something like the eye-fi but that can send any files.
Something similar to these devices :
http://www.infinitec.com/ (Why can't use : Will be released first of july which is too late for me )
http://www.hsti.com/ (Why can't use : Remote file system is mounted read only)