We were trying to create a custom device group on the lines of what is used in the geometrixx-gov site. The OOTB device group provided is /etc/mobile/groups/responsive.
Now the issue is that any custom device group with a name other that responsive like /etc/mobile/groups/custom is not detected by the page when in the Touch UI emulator mode. I do not know if this is a guideline as to only use the name "responsive" but it sure seems like a limitation.
Let me know if this is an issue or I am doing something wrong here.
In order to be able to use a custom device group on your page, you need to add it to the cq:deviceGroups property on the root of your website.
So say you have a website "my-site" under /content/my-site and a custom device group "my-site-devices" under /etc/mobile/groups/my-site-devices, then you can simple add the cq:deviceGroups property on /content/my-site/jcr:content/cq:deviceGroups. AEM will then pick up your custom group automatically.