It is the card that is present in some of HP's iPAQs and also in Toshiba PDAs.
Hacking the Imageon has some wonderful information for hard-core programmers who want to access the vid card directly for best performance:
Ever wanted to use the special features of the ATI Imageon chip in your PDA / Mobile / Embedded device? Unfortunately these features have remained "hidden" due to a lack of documentation, or information about the chips. These pages aim to start addressing this. They are based on work done for the Toshiba e740 and e750.
The site has been organised into features of the chip rather than just lists of registers. In some instances there is currently very little documentation - either because we have not yet played with that aspect of the chip, or because it has not been written. Each page contains what we know about each feature, and how to use it.