For areas you already know, a random route generator could be used to add variety. Additionally, the user would be able to mark certain stretches as "like" (e.g. a nice path down by a lake) and these be added in more often.
It also occurs to be that the same concept would useful for police patrols: to ensure full coverage; and to prevent criminals predicting where the police will be. The random routes for police could also be modified with crime data, so that hotspots are visited more often.