I seriously can't stop playing this… it's like when I first got Pokemon Blue. Although, I admit it's pretty much a Pokemon ripoff. (with a different battle system) However, this is what intrigued me...
"Your real world determines the kind of creatures you can find; your environment dramatically influences gameplay. Visit lakes or oceans to find water creatures. Stay up late to encounter dark and mysterious creatures. Anticipate changes in the weather to encounter creatures you can only find when it is cold, hot, clear or stormy. Be sure to explore! Many things affect what you'll find!"
It's only for iOS at the moment, but there's a notification signup for Droid users.