I actually made a plugin that does exactly what your looking for but sadly only 20 or so people used it on average so I stopped developing it. Its called "ReferGift".
If "we" don't support cracked games than how can you explain that bukkit doesn't have onlinemode default to true? Also, if you make your plugin only work on online server that would mean less users, a lot less. I also don't get the point of not supporting cracked games, why would you do that??
Bukkit does not endorse offline mode servers. Any plugin that sets it's aim to aid offline mode servers are not allowed. However, offline mode exists for debugging purposes, (like when minecraft.net is down or when you need to test actions that require more than one player.) It's useless to argue about the subject... If you really dislike offline-mode servers and do not wish for your plugin to work on such servers, do as some people above me has posted: Code:JAVA public void onEnable() { if(!Bukkit.isOnlineMode){ Bukkit.getPluginManager.DisablePlugin(this); }} Back on topic: I have made this a while back.... if no one posts one that will suffice, I will post mine ^_^ It has: IP Lock Configurable Rewards: Blocks XP Potions Special Effects Money (requires Vault) Permissions (requires Vault) Top 10 Refers It's a great idea =)
I posted this earlier ...... You will find most of the functions listed above already implemented with the plugin OnTime. http://dev.bukkit.org/server-mods/ontime/ You can find details for the referral functions here: http://dev.bukkit.org/server-mods/ontime/pages/referred-by-rewards/