The use of unauthorised portable electronic devices is explicitly forbidden on New Zealand registered aircraft during safety critical phases of flight. Other countries may word their rules differently, or may not have similar rules at all (although this would surprise me, a cursory search shows that U.S. FAR § 91.21 contains similar restrictions).
New Zealand CAR 91.7
91.7 Portable electronic devices
...
- (b) Except as provided in paragraph (c), no person may operate, nor may
any operator or pilot-in-command of an aircraft allow the operation of, any
portable electronic device on any aircraft flying under IFR during an
instrument approach or departure procedure or during any other critical
phase of flight.
- (c) Paragraph (b) does not apply to⎯
- (1) hearing aids;
- (2) heart pacemakers;
- (3) portable voice recorders;
- (4) electric shavers;
- (5) electronic watches; or
- (6) any other portable electronic device if the operator of the aircraft
has determined that the portable electronic device to be operated
will not cause interference with any aircraft system or equipment
in the aircraft on which it is operated.
- (d) In the case of—
- (1) an aircraft being operated on air transport operations, the
determination required by paragraph (c)(6) must be made by the
operator of the aircraft on which the particular device is to be
used; and
- (2) any other aircraft, the determination required by paragraph (c)(6)
may be made by the pilot-in-command or the operator of the
aircraft on which the particular device is to be used.