Solution:
You could try the WPTouch plugin… I use it for all my sites. But if you want a custom integration you might try iWebKit or something similar and redirect to mobile site.
WPTouch : http://wordpress.org/extend/plugins/wptouch/
iWebKit : http://snippetspace.com/projects
Or you could setup site as multi-site and have one subdomain with domain.com/m or m.domain.com If you have different functionality for each site.
The last two options would require a custom mobile theme. So in my opinion I would go with WPTouch.
Tom