and, no. i don't use sat nav for my morning commute. i've written a few applications enabling my phone to read books, news and other bits of information to me as i drive into the office.
I have in the past, for realtime traffic info and rerouting.
Cool, I didn't even know that was a thing yet (other than via old school radio broadcasting).
It's common on smartphones. There are lots of apps out there (Google Maps and Waze being two that come to mind) that collect real-time traffic data from their own users and public sources, and use that to find the most efficient route for you at the current time. Standalone GPSs can often do the same thing by linking to your smartphone and using its data plan to download the realtime traffic data. It can be really handy in a city with dense and variable rush-hour traffic.