There are various emulators, validators, mobile analytics packages and one mobile-specific keyword research tool available to help optimize a site for mobile devices. I won't list them all here, but I keep a running list in my bookmarks: http://del.icio.us/brysonmeunier/mobile_seo_tools

If you're interested in the subject beyond tools, I blog about it regularly at my Natural Search and Mobile SEO Blog: http://www.brysonmeunier.com.

Best,
Bryson