[Mitchell]

For this to b apporved you will need the following:
1. A plugin version cvar.
2. Checks to see if the client is not the Server

Suggestions:
A Reply to command to the server if it trys to run the command
A ReplyToCommand to the client when they run the command.
Set the killstreak to a variable, allowing it to be set back on spawn, so players can have it on until he puts in the command again.
Allow setting the arg of the killstreak to what ever the client wants.

edit: i've added on the suggestions below (untested)