There is also Locus Free (see the Google Market). You can download vector maps off-line for it to use. You can transfer your GPX to the phone and Locus will use them (tracks) to follow. Not really sure about its on the fly routing capability as I don't use it. Other options are OSMAND and Orux Maps; both of which can use pre-made maps off-line (different format than Locus).
All three of these apps are actively developed and are getting better all the time.
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