I can't believe anyone would hack away at their car's wiring to enable the use of sat nav on the move. It seem like hard work and could go wrong when all you would have to do is pull over to change destination.
You're right, I would never contemplate doing that and in fact, you no longer need to - as discussed in another thread, the latest navigation software from Lexus allows you to enter destination on the move.
What is incredibly frustrating however is the lock of the mp3 folders and inability to make phone calls on the move using the touch screen keypad - the former particularly so, as once you are moving you are unable to see what other tracks are on the CD ! I completely understand the safety / liability issues involved but the simple fact is that Lexus have deemed it to be safe, for example, to fiddle with the climate control function via the touch screen on the move, yet apparently it is unsafe to see what tracks are on any particular CD you are playing unless you are stationary !
At the very least, these functions should have been enabled for the passenger to be able to use !