Garmin should not need any introduction to those of you who have bought or researched GPS products in the past. Garmin has been involved in the app business for quite some time. It has a couple of decent apps for iPhone and Android devices. These 3 accessories let you get more out of your Garmin experience on your mobile device:
Garmin Head-Up Display Windshield Projector: displays speed limits, traffic, directions, and safety camera alerts on your windshield. It works for Garmin StreetPilot for iPhone or NAVIGON mobile apps.
GLO Sensor: provides you with GPS data on your smartphone and tablet. It offers better and faster GPS performance. It has up to 12 hours of battery life.
Garmin iPhone 5 Designer Car Kit: a bounce-free windshield mount for iPhone. It also lets you charge your phone as you drive.
If you use Garmin apps to help you get around, you might find the above accessories useful. It goes without saying that there are cheaper options out there.