Reading the regulations, the advise notes, and other published information (see section 6 of
http://ntl.bts.gov/DOCS/91-21_1.html as an example), it appears that the use of almost ANY electronic device including a hand-held calculator is prohibited by all international cariers not only on the (foolish) grounds of interferance, but also in case items get loose and bounce around.
I imagine a 505 in the back of the head could be fairly nasty. But then, would it be any worse than say the latest Stephen King book in hardback?