looks like pants and jackets of the near future will feature Faraday cage pockets - switching the tracking on/off will be as easy as just moving smartphone from regular pocket into the Faraday one.
So I do think this is a cool idea, though I have found that my phone usually gorges on battery power when it isn't in range of a tower (I'd love to hear the exact reason it would if anyone knows). An "airplane mode" pocket sounds handy and interesting, but I'd hate for it to drain my battery while the device is desperately trying to phone home.
That's a brilliant product idea, I'd happily buy it off the shelf
There are pocket sized Faraday cage pouches, you could sew them into whatever pocket you want.