KickDeath
Very lightweight and should work on all Bukkit and/or Spigot versions.
If installed, it will kick a player with a custom message when they die.
I made this plugin upon request from the Bukkit user RPGCraft
Permissions
kickdeath.exempt - Players with this permission node will not be kicked, same for OPs
Install
Just download and drag the .jar to your plugin folder. The configuration file will be created.
This plugin is commandless, so a config change would require a server restart or /reload.