I gave into temptation the other day and bought some Nike+ runners and the iPod extension thing so I could run and get feedback.
I've turned into a bit of a shoe freak, so I actually ordered one of the Nike ID shoes where I could customize everything on them (this included getting my GamerTag ("Feral Joe") printed on them).
I actually read the manual for the shoe insert that wirelessly transmits to the iPod receiver and came across this delicious warning:
"Important: Put the sensor to sleep before taking it [iPod sensor] on an aircraft, to comply with applicable government regulations"
I laughed when I read this. Can you imagine the looks you would get if you were in the waiting area for a flight and pulled off your shoe, removed the insert, grabbed a small high tech looking device from the shoe and used a paperclip to press a button on the sensor. If you were lucky you might be able explain, otherwise you might be in for a nice chat with a TSA employee.
And don't even think about doing that on the plane itself!