"Unfortunately is the application for the iPhone device related, that means actually you had to buy the application for your wife aswell, that is the reason why it does not work, sorry for that."
In trying to purchase traffic for my wife's iphone, I kept getting an error message saying that I'd have to purchase the app itself for this device. I emailed Navigon, because Apple's SLA states that you can put apps on up to five computers for home/personal use. The above quote was Navigon's response. I thought this is BS, and opened a ticket with itunes support & emailed them Navigon's response to me. I said I'd post back when itunes support responded. Well the good news is this: iTunes, in an email to me, said that apple, not Navigon, controls the SLA and to ignore Navigon's response because it is not correct. They further stated that yes, you can put traffic on your wife's phone at no additional cost. They advised me to make sure that on her phone, it is signed in to my store account, delete the app from her phone, also to make sure to add the app back through itunes with the phone connected to the computer and signed in to my itunes account. Once done, I should be able to add traffic with no problems. If the update doesn't work, to contact them and they would advise further. So, bottom line, yes you can get traffic on multiple devices without having to pay for it.
Sad fact is, I'm not very impressed with the traffic update & doubt I'll go to the trouble of putting on my wife's phone, even after going through all of this with Navigon & itunes support.
This is quoted from itunes support:
To change the account you are using on your mobile device, go to your computer and sign in to the iTunes Store with the account you want to use on your mobile device, then sync your iPhone or iPod touch with your computer again. This will transfer the new account information to the mobile device. To sign in or out of an account in iTunes choose Store > Sign In (or Sign Out).
