I have this in my J1.0.15 sures too.
Is perfect for switch from default template/home to pda dedicated ones.
I've hacked the code to switch for pda and iphone differently.
Just a note for a little bug in Jommla 1.5 version
$mainframe->setTemplate($template);
does not affect any template change in Joomla 1.5.
Substitute this command with
$mainframe->setUserState('setTemplate', $template);
... And all works...