good example of creepy vs value by @Kevinmarks "marauders map vs the weasley clock" in Harry Potter
I have written about the boundaries between value and creepy many times - are few examples are linked here, however this is a good one as it shows that one is about detail, moving, real time and what others can find out about you without you knowing - the other is about sentiment
What is interesting is that both require the same level of detailed knowledge, it is all how it is presented that makes one acceptable and one creepy...
The Marauder's Map
The Marauder's Map is a magical map of Hogwarts created by James Potter, Sirius Black, Remus Lupin and Peter Pettigrew while they were at Hogwarts, during which time they gained extensive knowledge about the school grounds, such as its various hidden passages, from their frequent night-time adventures together.
At first glance, the Map is simply a blank piece of parchment; but when the user points his wand at the Map and says, "I solemnly swear that I am up to no good!", the message "Messers. Moony, Wormtail, Padfoot and Prongs, purveyors of aids to magical mischief-makers, are proud to present the Marauders Map", and a detailed layout of Hogwarts appears, including its occupants, secret passageways (and instructions on how to access them), and other mysteries, though several locations like the Room of Requirement and the Chamber of Secrets do not appear on the map, either because the Marauders did not have any knowledge of them, or—in the case of the former—they are Unplottable. Furthermore, Animagus disguises, Polyjuice Potion or Invisibility Cloaks cannot fool the map, as shown in Goblet of Fire when Barty Crouch, Jr. (disguised as Moody) breaks into Snape's office[HP4]. Saying, "Mischief managed!" returns the map to its original blank state.
Weasley family clock
The Weasleys have a special clock in their home, the Burrow, with nine hands, one for every member of the family. Instead of telling the time, the clock reveals the location or status of each family member. The known locations are: Home, School, Work, Travelling, Lost, Hospital, Prison,Quidditch, and Mortal Peril. The Weasleys are the only family mentioned in the series to own such a clock. Dumbledore calls the clock "wonderful" and seems impressed by it, suggesting that it is an extremely powerful object.