One of those nifty system monitoring packages, with all the buzzwords you'd expect. Watches systems as well as applications. Has a dashboard, which I think you can disable. Realtime, too. Supports third party extensions and applications. Tries to use as little RAM as possible, tries to carry out as little storage I/O as possible. Claims to have a web API. Zero dependent packages.
Can notify through multiple means, including IRC, email, Pushover, and custom endpoints.
There is an OpenWRT package called 'netdata' which can be installed normally.