Dumbledore left Ron the deluminator that he invented. Originally, we see this device in the first book when Dumbledore uses it to suck out the street lamp lights. We’re lead to believe that all this device does is absorb light, and return light, but Ron Weasley finds the device true purpose when he’s separated from his closest friends.
While thinking about his friends, when they mentioned his name, he was able to hear their conversation through the device, almost like a radio! The magic doesn’t stop there, as the deluminator will also revealed where his friends were, and gave him a ball of light to use to apparate right where they were located! This happened a couple times, but that wasn’t the mind blowing part.
If Dumbledore had this device all this time, whenever he was thinking about someone close, and they were talking about him, could he also hear them like Ron did? Wow, because if so, he must have known/heard alot about what Harry thought about him! Perhaps it was even this device that called Fawkes to Harry to save him in Book 2 when he was battling Riddle and sticking up for Dumbledore?!
The CIA got nothing on Albus Dumbledore!