Here's the song, entitled, "Satellite Heart" by Anya Marina. Marina, apparently a Twilight fan (like the rest of us!), reportedly said, "This one's for Bella", on her Twitter page.
Check out these lyrics:
"I'm a satellite heart/lost in the dark/I've spun out so far/You stop, I'll start/but I'll be true to you/no matter what you do."
Yep, sounds like Bella to me...