I just discovered an amazing (free) Wordpress theme for iPad (maybe it works for other tablets too, but at the moment I've no way to test with anything different than iPad. I know, it's not so useful to use a specific theme for a tablet, because the normal site, if it is well formatted, it's perfectly shown on tablet screen; but in this way your blog/website is shown as "native tablet application": read articles on your blog will be like read an ebook :)
Anyway, if you want to make some tests, the plugin I found is Onswipe you can see a working version browsing my blog on a tablet (let me know if you can see it with an android tablet :P). You can check result looking the photo in this article.
A thing I'm thinking about is that in this way (iPad theme, mobile theme, normal theme) it's impossible to control how your articles will be shown to the users... I check some articles I wrote and seem ok an all devices, but I've just simple text articles with some "code" information (well displayed just on the normal website).
Is it a good choice to have separated themes?