PocketDOF is dedicated to photographers who want to calculate the hyperfocal
distance as well as the depth of field according to your configuration (camera,
lens) from your WM device. 
So what's this for?
The hyperfocal distance is used mostly on the field and represents, given a
configuration, the distance from which everything will be sharp. Once your lens
is set to that distance, you don't have to touch it anymore and hence you will
be ready to shoot instantly.
The depth of field, well it's the area of sharpness in front of your camera. It
depends on the lens focal distance, f-stop and the distance to the subject too.
For example, with a 50mm/1.8 mounted on Nikon D40X three meters far from your
subject, the DOF is 25cm. Pretty useful to know especially when you don't have
an autofocus enabled.
The application is currently available for windows mobile, either
smartphones or pocketpc (with a .Net compact framework). It will very soon be
available for android and Bada too. PocketDOF is worth 2€ and can be purchased
via paypal.
You will find it at caketuzz.com, my news
website for mobile software.