Child Themes not fully supported

Good work so far.
But child theme functionality is not fully supported (yet, I hope!).
Customized functions inside functions.php of parent theme (template) are not found when child theme is called via your plugin.
This (for me) is very annoying because I have lots of customized functions in my desktop theme which now I have to copy and keep updated inside the mobile child theme now.
Any ideas?
Or am I doing something wrong?

http://wordpress.org/plugins/device-theme-switcher/