Auto Switch Theme according to user agent (mobile/iOS)

[mattewre]

(moved from http://www.simplemachines.org/community/index.php?topic=471480.msg3295362#msg3295362)

Can you suggest a way to auto switch a theme according to user agent of users, for example from smartphone (essentially iOS)?
everything brings to http://custom.simplemachines.org/themes/index.php?lemma=2089
but the mod seems not working on 2.0.2 (the theme is quite ok instead)
suggestions?