BZZZZZZZZZZZZZZZ wrong! I love that rumor though.
Actually, a Bungie spokesperson already spoke on this rumor at CES this past week, and said there is definately NOT going to be a Halo game in any form on the Gizmondo. The Gizmondo's "big name franchise" they'd been hinting about making an appearance actually ended up being Sonic the Hedgehog, but actually it ended up being more, as apparently Sega will release a collection of it's 16 bit/arcade hits for the Gizmondo shortly.