I have a wordpress site and want to create a different theme for mobile. I'd like to create a subdomain such as m.domain.com which will use a mobile optimized theme much different than the desktop version theme. I understand multisite will handle the subdomain problem but I want all the content, custom posts, plugins, etc to be in a single site in the admin. 

Is there anything out there that will allow me to create a mobile subdomain and have a separate theme applied to that subdomained site while keeping the content, posts, plugins in a single site in the admin? 

Thanks!