@F3G:
The regulatory agencies mandate that iPods, cell phones and laptops be turned off
during take-off and landing, be done so not because they interfere with an aircraft's systems but because in the case of the first two, the user may not hear CC instructions in case of an emergency. In the latter case ie, laptop use, also because of distraction but also because it MAY interfere with aircraft systems especially communications.
However, the jury is still out in the interference case.