These are two ride "meters" I like and use that are FREE apps for your smartphone:
"DigiHUD" and,
"Polaris Navigator".
I don't have any personal or financial interest in either app or their developers.
DigiHUD gives me real-time speed and distance data and stores statistics for up to 3 separate rides. Shows average and max speeds during ride, and also lets you set an SPEED LIMIT ALARM (sound and visual). Also displays your compass heading.
The visual appearance is SIMILAR to a panel meter such as a "KT-LCD3". The not-for-free version has more features.
Polaris Navigator gives me the same data but in a smaller format...however, Polaris Navigator also gives me real-time navigation, including waypoints. There are many free maps particularly for the U.S. that Polaris Navigator can load and use (topological, street maps, satellite view, etc). The Open Source street map provides amazing granularity and detail for major cities. You also get altitude.
You can check the Google play apps store to examine details on these apps and differences between the free and not-for-free versions.
I've been using them for a couple years and have not been hit by any spam as a result.
For longer trips, you're going to need a power source for the phone. The display takes a lot of power, especially during the day.