Tracking Opens on Mobile Devices

I understand that when a mobile device opens an email, we add to the open count, but we want to know the breakdown of how many opens are on Mobile Devices and what kind.  It would really help us design our emails knowing what percentage of our customers are reading our emails on iPhones, Blackberries, etc. vs. using Outlook on a laptop or desktop.  Also what % open the emails in a browser.