Anecdotal sources suggest that in Pokémon HeartGold, Eevee can evolve into Espeon when leveled up with maximum happiness.
Give it loads of vitamins and give it haircuts daily. You can get vitamins at Goldenrod Department Store.
You can walk around with it and give it a soothe bell to give happiness gain an upgrade.
In latest buzz, Niantic Labs has released a new Pokémon GO update which adds the Pokémon Appraisal feature. Players will be able to use it to learn about a Pokémon’s attack and defence capabilities, as measured by their Team Leader. Find out more at Gamespot.com.