I just got put onto a brilliant app for android users. Photo Tools Pro.
Some of the things it has:
DOF and hyperfocal distance calculator
Field of view calculator
Exposure reciprocation calculator
Multiple exposure calculator
Exposure Meter (uses you phone camera to come back with aperture/iso/shutter speed for the scene)
Sharpening calculator (uses viewing distance and print resolution to give you an idea of how much sharpening to apply, for prints)
and more. So if you are looking for a good Android App for your photography, take a look. It costs $1.92 for the paid version (called the donation version). It is probably the most comprehensive App I have seen.