Ask HN: System uptime monitoring software?

Digital Ocean's interface shows disk I/O, CPU, memory, disk usage, process list, and bandwidth total. It's nice to have without having to tunnel in every time. Sometimes I just want to have a quick glance without running through lines of text (not to say I don't enjoy that, of course!).

This would apply to my personal project(s) and time, so there is no need to be concerned with full-scale deployment. Under a FOSS license and a decent UI (or well enough put together), what options are there to consider?