The same question arises here as arises in every other "replace your GPS with a cell phone" thread: can you import a custom .gpx route into your phone (like the kind you'd create on software like Tyre), and then have your phone follow that route, give turn by turn directions, ETA, etc? For most of my rides, the shortest route isn't the one that I take. On the Google Maps app on my phone, it only allows you to input a starting point and end point. If you input a custom map you create on your computer, you can see the map, but the GPS won't follow it, and you don't get turn by turn directions.
So far, the only app I've seen that does what I need it to do appears to be OsmAnd, and the free version has its limitations. You only get seven free map downloads, you have to download each state separately (which I think means one download per state), and they take up memory space on your phone. From the reviews I've read, OsmAnd has a less than intuitive user interface and can be clunky to use. I did get a Google Play card so I could download the paid version and experiment with it, but just haven't done it yet.
I know that Macdoc has the impression that some of us are Luddites because we still use a GPS. Maybe so. However, I can create the most meandering route I can think of on my computer using Tyre, with 1000 different waypoints, plug the Garmin into my computer, press the "send to Garmin" button on Tyre, and the route is loaded onto my GPS. My GPS will then follow that route, calling out turn by turn directions, ETA, remaining miles, etc. So far, I haven't read about a single phone GPS app that will do all that, and do it that simply.
If I only ever wanted to go from Point A to Point B by the shortest possible way, I wouldn't bother with a GPS and I'd just use a phone. That's rarely the way I go. If there's a phone app out there that can do it as simply as the "push one button, send map to phone" process I use now, then I'm sold.
Note to Brian: Thanks for that speedometer app. When I have to use my tankbag, I need to extend my phone mount to the point that it blocks the speedometer display. This solves that problem.
"No matter where you go, there you are."