I'm using WPtouch version 1.9.33 and WordPress SEO by Yoast version 0.4.2.
WPtouch does not seem to honor rewritten <title> tags in WordPress SEO. Regardless of what is defined in WordPress SEO, WPtouch will append the site name to the end of that custom-defined <title> tag.
One way around this is to set the custom site title in WPtouch as a single space, but then the site title isn't rendered as content at the top of each post/page. I was wondering if you could code in support for this very popular SEO plugin.