There currently isn't a way to see in some fashion what percentage of your total page views, visits, etc are from mobile. You can see mobile trending against itself but not against the whole.
Once in this report, I click "Showing" and change the metrics it provides from Mobile Views to Revenue, Orders, and Mobile Visits.
Currently, I can pull Revenue and Orders as Mobile Revenue and Mobile Orders compared to Total Site Revenue and Total Site Orders over specified time periods. Yet the Mobile Visits Metric shows the accompanying penetration percentages as a percent share of the total Mobile Visits. I would really like to be able to compare Mobile Visits to Total Site Visits in one report (without having to manually pull the data from the Visits report and manually calculating the Mobile Visits Penetration = Mobile Visits / Site Wide Visits).
This is definitely something I am looking for...on sites that aren't running a mobile version of a website, it'd be great to instantly determine if the percentage of mobile views is changing (not just growing/shrinking relative to itself)