yeah this would be possible client-sided.
It'd be possible without server support I'm pretty sure, but server support may make it better. I'm not sure if ghosting would make a difference if it were entirely client-sided or not, but I'm guessing it would.
So if I made this I'd have the normal client script then also a server-sided part that you can turn on for your server so people who have the client mod get a more accurate number. That is, if ghosting would affect this.