Rusty
If one gets the iPhone that has cellular data and not just wifi it will have a GPS chip in it.  It is a very good chip set and works almost as good as my Garmins. It is the same as the iPad. I use the GPS in the iPad along with the Forflight app to fly all over the south west and Mexico.  chip

I didn't know that!  I was told otherwise.  I Googled it, and read a great article Here: http://tewha.net/2011/10/how-the-iphone-gps-differs-from-a-standalone-navigation-gps/

The writer claims that the iPhone does have a GPS chip, but it's dependence on the cloud for mapping is it's weak point.  If you find an app to map independently of the cloud, an iPhone would be a terrific ADV GPS.

Of course, you'll wanna armor up and waterproof an iPhone, but there's plenty of options out there.  Also, you'll need a charger running from the bike's battery--according to the article, an iPhone uses a lot of battery when it's in GPS mode.

Thanks Chip, a little late for me  , but thanks anyway.