Question: I know there is `tail` which tracks if anything has been appended to a file.

I also know its possible to do using vim `:w !diff % -`

Is there something similar which tracks if anything is modified in a text file and prints it out.

To clarify is the something similar to tail but the change within the file might be anywhere. (Rather than me having to run vim everytime.)

Answer: 
you could try `watch -d cat file`.

See `man watch` for more information.
`tail -f` should be all you need, or am I mistaken?

EDIT:  

Scratch that, you want a solution for things changing but not just through appending.
Sadly I just found out I cannot delete my own posting...