Hi,
I have experimented with this and have some suggestions.
If you use module mod_mj_header (from the backend Extensions > Module Manager )
you can set the text to be
<a href="http://www.sitename.com/">{{sitename}}</a>
(This may not be efficient)
you will need 3 copies of the module and publish in
mj_imode_header
mj_pda_header
mj_wap_header
The iphone is a special case and is complicated.
The sitename is inserted in either
packages/templates15/mobile_iphone/index.php (in the tar package)
or
packages/templates16/mobile_iphone/index.php
div class="toolbar">
<h1><?php /** @var JSite $app */ $app =& JFactory::getApplication(); echo $app->getCfg('sitename'); ?></h1>
and you would have to hard code the sitename into the code and remember to maintain it.
div class="toolbar">
<h1><a href="http://www.sitename.com">SuperSite</a></h1>
Anyone else feel free to contribute to the thread.