This is an interesting game, Ingress. It recently came to Apple / iOS devices and has been on android for some time. Crudely describing this game, think of it as a real world Capture The Flag. Now you see why I like it.
Your GPS coordinates will relate to a map of the actual cities you are in. This is an international game, with chat mode defaulted to your local region. Global chat is fun, but very fast paced.
Walking around, you will see Portals and items. Blue Orbs are XM (Energy for actions), while you will also occasionally see keys. Click on keys to acquire them from the world map. As for Portals, you will see Green, Blue, or Silver. Green are Enlightened, Blue are Resistance, Silver are unclaimed.
Items can be obtained by hacking any color portal. Weapons are used to attack other faction portals. Attacking uses up XM, just as placing portals and support items on portals will do. Linking portals is also an option when you have 8 generators on a portal, so be sure to do that for XP. You can also upgrade generators on portals, if you have higher level ones. Otherwise, you can repair damaged generators, if unable to upgrade them to a higher level.
Since we live in a GPS tracking based world, you might as well have fun with it. :p That's what I'm doing. I am currently Level 5.