Questie is an outdoor GPS quest app for Windows phone 8.1. In the app, you are guided by GPS to accomplish the quest. You can create the quests using their website questie.net where you can invite participants to follow a quest. It installed quickly on my Lumia 535 and ran perfectly.
Then the participants of the site get an email containing the link to download the app that also includes a quest code to download the app.
Or you can let someone make a quest for you to follow with your Windows Phone and go outdoor on a nice sunny day.