That's pretty much what Albus Dumbledore's pensieve does for him. Except, to go even a step further, it lets you be in the scene as an observer, rather than just watching it from the outside.
"I sometimes find, and I am sure you know the feeling, that I simply have too many thoughts and memories crammed into my mind."
"Er," said Harry, who couldn't truthfully say that he had ever felt anything of the sort.
"At these times," said Dumbledore indicating the stone basin, "I use the Pensieve. One simply siphons the excess thoughts from one's mind, pours them into the basin, and examines them at one's leisure. It becomes easier to spot patterns and links, you understand, when they are in this form." (The Goblet of Fire, 597)Dumbledore uses his Pensieve to teach Harry everything he knows about Voldemort's past. When he attempts to show Harry something from Slughorn's memory about Voldemort, it becomes obvious that the memory has been changed. In the midst of a normal replaying of a memory, "the whole room suddenly filled with a thick white fog, so that Harry could see nothing but the face of Dumbledore, who was standing beside him. Then Slughorn's voice rang out through the mist, unnaturally loud, 'You'll go wrong, boy, mark my words'" (The Half-Blood Prince, 370).
Dumbledore explains the phenomena: "'As you might have noticed,' said Dumbledore, reseating himself behind his desk, 'that memory has been tampered with'" (371). From this experience, we learn that we can trust the memories shown in the Pensieve.
With all the mystery surrounding Snape and what his true loyalties were, it is important that he give Harry his memories, rather than his words, to prove his goodness.
The Pensieve showing Harry the dying thoughts of Snape is so powerful of a message that Harry ends up with a high respect for the man. He even names one of his children after him, and tells Albus Severus that he was named after "the bravest man I ever knew" (The Deathly Hallows, 758).
Tomorrow in my Harry Potter themed A - Z post, I will be featuring Quibbler - a questionable wizarding news source.