Ripoff of
Frequency with Dennis Quaid and Jim Caviezel. Swap the father/son relationship with an uncle/niece one and cut the time shift from a couple of decades to a couple of weeks a and BINGO! new movie.
shareThis has been done many times. As you mentioned Frequency (2000): ham radio/30 years. But that was not the first either.
There was also Twilight Zone (1985.6): telepathy/285 years. A teenager with a fever is suddenly able to communicate telepathically with a girl from 1700 who has also fallen ill - and because of what she starts saying they want to kill her thinking she is a witch.
But reducing the time difference to a couple weeks could make this more urgent and introduce some new twists.