If you can, it might be worth tying different templates to different subdomains dedicated to mobile devices, similar to what Google and Yahoo have done.
I started with that approach. Unfortunately, we're still in the infancy of mobile-friendly blogs so detection of handheld devices, auto rewriting of URLs, auto-publishing of both templates, etc -- it's just not available in a easy template you can install and push the go button. I gave it a try and spent several hours trying to write such code (never did blog template development before so I often had to guess on the syntax). But after not much progress, I decided it would be easier to refine a mobile-only template and then add tweaks to detect larger screens.
So at this point, I'm still backporting elements from a regular template into my mobile template to first get to the refined stage.