Okay, I found my ghosts, I have my creepy little heart. Now what? I can't do much with it.
But what if I could?
What if I could eat the heart?
Then what if I got a new ability, the ability to place one ghost somewhere. And every time somebody found my ghost, I got xp for it. If I hid my ghost in an obvious place I would get fewer xp than if I hid it in a less-well-traveled location. (There's probably some complicated algorithm that could figure out a correlation between hiding place and # of xp rewarded.) And then, after my ghost has been found 10 or 25 or 100 times, I get an extra big helping of xp and my ghost fades away.
And as an added bonus, after I eat the heart I would get some "Braveheart Blue" streaks on my face for a small amount of time.
To show that yes, I am brave enough to eat the heart.