It is probably not the kind of application you are looking for... but maybe worth trying. I mean sport trackers like Endomondo, Runtastic, Strava and others. At least one of these I know better - Endomondo is a combination of a sport tracking application and social media. When you are a passionate walker, you may register your walks with this application and share them with your friends around the world. Unfortunately it's not easy to find a walking partner in a specified area. A few years ago they were presenting maps with the position of each active user, but for obvious (security) reasons they don't do it anymore. They had also a possibility to register your own events - define the track and the date of the walk and make it available to everyone who would like to join you... but they deleted this feature too.
Anyway it's still possible to take a part in challenges (who will walk more kilometers in a specified period) or create your own challenge and announce that you are looking for walkers in this area.
BTW It's a nice opportunity to communicate with people in many languages too.