Can this be modified to allow you to have different styles on different subforums?

Yes I did, thank you.

You can already assign a style to a [sub]forum with vanilla vBulletin ...

I had the same problem, and solved it here:
http://www.vbseo.com/f2/base-href-23196

I've installed this mod and it is working perfectly, allowing me to go to a mobile skin via a sub domain.

However I also have the same issue as mentioned by Jase2. From the admin panel, when I go to vBulletin Options and scroll through the Setting Group list, an entry for DDDS is not shown. However there is a completely blank entry in the list and when i select this it goes to the DDDS settings page. Therefore it looks like it is adding the entry correctly into the Setting Group list but not adding a title.

I finally found and fixed the name not showing up in vBulletin options - simply reinstall and overwrite existing...

Great. Thanks. That fixed it.

Nevermind....found my answer about vBSEO above.

I must be the only one this isn't working for :(

I setup http://m.bayoushooter.com/ to forward to http://www.bayoushooter.com/forums and the redirect works so I installed the hack, turned it on, put "m.bayoushooter.com" in the domain name field and chose my mobile skin but when you go to m.bayoushooter.com it redirects but uses the default skin.

You shouldn't be using redirects as it does as the name implies, redirects you to the destination domain and as such this add-on won;t kick in.

You need to point or park your m.bayoushooter.com subdomain on the same webspace as your standard domain.