Will OpenX deliver ads to Mobile (Cell) Phones?

Yes, however it depends exactly what kind of banners you want to deliver and what technology the mobile devices you are targeting will support

The simple solution is to treat a mobile device like an email — assume that it won’t support your javascript code or advanced html.

In this sense, create a zone as an Email zone. Assign 1 active Image banner to it. Generate the cookieless image tag, and this will display on your mobile device.

[1] http://www.openx.org/en/faq/features-and-functionality/will-openx-deliver-ads-mobile-cell-phones