Smartphone GPS Navi over radio

[stevejinde]

Now I have just come back from a tour here in Germany in which my mate was using the latest BMW GPS system which is in fact Garmin. The Garmin caused all sorts of problems. It might work well in the States but, I have heard about it having problems over here. Enough for me to think about something else and with Garmin closing down all their mobile apps, well... o I thought I'd look at Tomtom. However they don't have an audio jack and so will not work over the radio. Smartphones do have a audio jack so I thought of running the Tomtom Go app on my phone and, using the GPS Audio adaptor, running it over the radio. Has anybody tried that? Does it work? And if not,(it should in theory) why not?
Regards Steve.