Plotfree is a simple, and probably inaccurate tool for monitoring memory usage, which I built to help me figure out when I've outgrown my droplets at Digital Ocean.
Usage is fairly simple - set up some kind of cron job to run
plotfree-update.py (you'll need psutil installed to run it)
periodically, and point a web-server to the public_html folder. All
requests are for static assets, so deployment should be trivial.
You can see it in action at https://memory.dominicrodger.com.