Bukkit

Using the Ping-Tool you are able to detect player with high ping. But why is a high ping bad? The ping is basically how long it takes for a data-package to travel from point a to point b (e.g. your computer to the Minecraft server) this measurement is taken in milliseconds (0.001 s) so a ping of 1000 ms and higher should be OK for building stuff, but for PvP I recommend a max ping of 500. Because if you'r opponents ping is e.g. 1000 and you punch him you'll punch him at the position he was 1 second ago. Although I think Minecraft is displaying the latency instead of the ping. The latency also counts the time it takes the server to work on the package and send an OK back to the client.

For this simply use the /ping command:

In the config you're able to set if the ping should be visible in the scoreboard (use_scoreboard). It uses the main scoreboard and may get hidden for players by other plugins. Also you can define how often the ping will refresh (ping_delay).
Also you're able to set a maximum ping (kick_maximum). If a players average ping exceeds this limit they will get a few warnings (kick_warnings) and finally get kicked. This warning has a separate delay (kick_check_delay) that should be a multiple of the normal ping (ping_delay) interval in order to collect an average.
Disable the ping kick by setting the kick_check_delay to 0.

Op yourself or give you the ping bypass permission to prevent yourself from being kicked for high ping in case you you set the max ping to low.