little iphone helpers - recommendations?

just installed photobuddy (iphone.ambertation.de), a handy little app for the iphone. helps with calculating hyperfocal distance, ev/f/iso-combinations, flash calculations, offers even a sort of digital grey card and you can use the iphone to measure distance to objects. do I need all this? don't think so ;-) but I love my iphone and I love using it.

what about the ipers out there - does anyone know about other useful apps or features?

(for example, I store all my manuals - cameras, flash and so on - on my iphone... just in case!)