I might be. Even more, if you could come up with a cover (hinged or pop-off or slide-off or whatever) that could take advantage of the hall-effect sensor.

I've got an ancient Casio calculator, and kind of like the hard cover that protects the front of it when closed. Here's a picture of one:



I dunno if anybody makes covers like these for modern mobile devices...

EDIT: even better, if you could add a pocket somewhere for an SD card or two.