Several years ago, while in the military I had our chief executive's limo on board along with the guard detail, during preflight I noticed all of the vors and adf needles swinging randomly and the hsi turning continuosly...asked our load to go down and check if the guard detail had any electronic equipment turned on, in fact they did and when the equipment was turned off everything returned to normal.
A few years back on an A320 we were stopped at the end of the runway waiting for some storms to pass, a jump seat rider...a tower controler...asked if she could use her cell phone, I didn't think it would be a problem, but as soon as she started dialing it caused massive interference with our radio which was on ground...so much that I was unable to hear ground control; when it was turned off the interference went away.
Again on the A320, we were shooting a visual approach and had the ILS tuned up, the localizer kept breaking lock, asked the FA to check in the back, and she found a computer on, after the computer was turned off no further problems.
I guess I just do not see the need to take a chance with any possible interference...wait until you are on the ground.