Well, I take that back. I emailed one of my professors (I'm studying mobile development) regarding jQuery Mobile. I was wondering if all the bells and whistles I'm adding to my projects (which I was later planning on adding to my Zen Cart designs) were a waste of time or not.
We went through a lot of JavaScript instruction obviously to learn the concepts but then it was more convenient to rewrite everything for jQuery and jQuery Mobile. I certainly do not feel like rewriting all the work I have done once again when we go into more detailed iOS language like Objective-C. So, next month, I will be introduced to Objective-C and I'm told that I will not be writing anything with Javascript, HTML, jQuery or jQuery Mobile.
With that being said, to better answer your question. If you want to create mobile templates for Zen Cart, I seriously recommend jQuery Mobile, it is easy to learn and the design can be displayed across several mobile platforms. In that manner, the template since it is a webpage will be able to open in an iPhone, Android, Blackberry or whatever device the visitor is using.
PhoneGap, which is what I'll be working with next month, is in my opinion more of a device specific tool. Meaning, if you create a Zen Cart app for iPhone, you will also have to create another one for Android and so on...
You have to consider the updates as well. Let's say that you find a bug in your jQuery Mobile design. You fix it, upload it to the server and finish. An app, you have to fix it, submit it for approval, notify the users of an update and hope that they actually update your app.
If you want to build a headache free Zen Cart website for mobile, use jQM. You can also experiment with
Twitter's Bootstrap and create some
Responsive Web Designs. I have been experimenting with these as well and they are much easier to work with and there is even a much important benefit to it: "You only need one design". I understand also that the Zen Cart team will be creating a Responsive template for the upcoming
version 1.6. Below you can see how a responsive design adjusts itself to the screen size. I know the template is not really much to look at however, the point is to make the template flexible. With few additional tweaks, it should look very professional.