Geocaching is a modern day treasure hunt, conducted globally.  You will need a GPS (which many people have right on their phones) and access to the internet.  Geocaches are everywhere.  Anyone can participate.  There are a few rules, so make sure you read on line first at www.geocaching.com beforehand.

At each Maine State Park & Historic site, you'll find a brown passport station which you can unlock to collect different stamps for your passport.

Geocaching & State Park Stamps for Passport