Which algorithm, that is based on open Street map takes the current GPS position, a duration and an average speed or way of transport(by foot, by bike or by car) and outputs possible routes, that start and end at the current GPS position and fulfill all criteria? That means, you start from a GPS position, you move around till the time has elapsed and when the time has elapsed, you should be at the same place where you started.
You are in a new country. You just arrived at your hotel. In one hour you are going to meet a friend of yours. The two of you agreed to meet at your hotel. You decide to get to know the close surrounding a little bit by walking. At the same time you want to be back in time. You would like to not see the same road again when you come back. So you grant GPS access in your mobile device, tell the amount of time that you have and that you don't want to see the same road again if possible. Then the program should output a series of routes that you can walk that fulfill those criteria.