From http://open.silverstripe.org/ticket/6008

Allow for a ComplexTableField? so people can define which devices should receive a mobile theme. This would mean you can define a number of different themes for different devices.

For example:

Opera mobile, iPhone goes to "mymobiletheme" iPad and Dell Streak go to "mytablettheme"

Any mobile devices that don't belong in a profile would go to full site.

We should also allow an easy way for site developers to set their own mobile devices in the profile checkbox lists, as the default ones won't cover all mobiles by far.

We could also allow for all non-popular mobiles to go to another theme (or an existing one), so there's a fallback for old Nokia phones, for example.