which is from the csh.
The standard shell has type.
The ksh in SysV introduced whence.

I think the wrapper should cover all arguments

Code:

for f
do
  [ -s "$f" ] && cp "$f" "$f.bak" && echo "created $f.bak"
done
/usr/bin/vi "$@"
for f
do
  [ -f "$f.bak" ] && rm "$f.bak" && echo "removed $f.bak"
done

Unlike $* the "$@" can handle arguments with spaces. Some early shells have a bug, AFAIR the work-around was "${1+$@}"

Code:

vi "file name with spaces"

Last but not least, I think the best backup is built into vi and vi -r is a good recovery.