ChronoPay is a Bukkit plugin for rewarding players with money for online time. Originally made several years ago for a smaller Minecraft server I play on, I'm now open sourcing it and making it available publicly.
The plugin depends on Vault for economy features, and optionally Essentials to prevent players from earning money while AFK.
The plugin also includes an IP address check to prevent players from logging in on multiple accounts to earn money.
Please refer to the plugin's GitHub repository for most of your information about the plugin and updates. The README file details versioning, configuration, commands, permissions, etc.