I use my old iPhone purely for Strava, with airplane mode on. I have no contract so there's no mobile data on it anyway.
I just turn wifi on when I get home to sync the saved ride then turn airplane mode back on again. I do find Strava doesn't like syncing like this so I normally have to fully quit Strava (from double-clicking the home button) then restart.
I used it for navigating a route I'd built on Strava yesterday. You can see the route and your progres against it. There's no actual map -- you're just looking at a line against a white background with your position marked, but I didn't actually find this to be a problem.