Not the more normal FOSS project, but I keep plugging away on Speeduino an open source (hardware and software) Engine Management system (aka ECU). Started it way back in 2013 and it just continues to grow in terms of community and contributors.

We have no way of accurately tracking how many are in use, but there's at least 4000 of these units out there these days, which is a number I'm pretty proud of for a hobby based open hardware project.

You still had savings?