If you take a look at the iPhone page (http://dofmaster.com/iphone.html) it says: Open http://iphone.dofmaster.com on your iPhone or iPod Touch to use the web app.dofmaster.com claims to have one for ipod/itouch.
Lining up the infinity symbol with the aperture markings on my lenses works pretty good, too, by the way.
Both of these are widgets and only work on "real" Mac OS computers. I knew and used the first one and just installed the second one. Funny thing, I don't get the same results on both of them !!!