* Screen lock function, to avoid accidental keypresses when using the GPS in a non-driving situation (for example, putting it in your pocket while walking).
* Debouncing of keypresses on screen, to avoid "typos" when trying to use the GPS on a bouncy road and accidentally hitting things with your nearby fingers
* Display altitude!
* In 2D display mode, disable auto-zoom
* In 2D display mode, allow panning around the screen by dragging and dropping fingers
* More Favorite locations! The limit of 32 is just way too small.
* Show 2 upcoming maneuvers on screen, not just 1. This will help when driving through unfamiliar areas and having to quickly make a lot of turns.
* Group together highway segments that are on the same stretch of road, so the user sees a total 50-mile segment, for example, instead of five different 10-mile segments on the same freeway. The "Disable keep left" function doesn't quite work all the time.
* Scrub your data. In the Bay Area, for example, there's "I-880 NB", "I-880 Northbound", "North I-880", and so on. All refer to the same road. Different segments have slightly different spellings, and this is sloppy.
* Show the frequency that RDS-TMC traffic data is tuned to
* Show the subscription renewal date of the user's current RDS-TMC subscription (if this data is available)
* For the "thermometer" traffic column, please color-code the thermometer by congestion level (red, yellow, green), instead of treating congestion as an incident with a single icon
* Build in a compass, like the iPhone, to avoid the problem of the GPS not knowing what direction you are facing when standing still (or powering up the GPS for the first time).
* Real docking station available, for professional car installers to use. It would hook into the car's already existing FM antenna (for RDS-TMC traffic, and FM transmitter of voice), and the car's 12V power, and perhaps an external GPS antenna up on the car's roof, and no cable clutter at all (everything would be behind the dash).