Don't you just love this idea- and this iPhone app looks great, too.
For 8 bucks you can buy yourself the Swiss Army knife of DSLR-shooting. (although certainly not limited to DSLR's). Main features:
Electronic Slate
Viewfinder
Daylight hours
Shot log
Depth of field calculator
Spirit level
There's more in-depth information at the website. It's a Beta-release; on the website a few functions are mentioned that may behave 'erratically' but the developer seems to be serious about fixing these issues. It's to his credits that he mentions the shortcomings.