Mozilla heka. As far as data collection and processing goes, we are still stuck with Logstash after all of these years. Heka promised a much more efficient solution, being implemented with Go and Lua plugins.
I never understand why people are so fixated on battery runtime. If you actually use the device indoors, don't you have a possibility to charge anytime. For me, I alternate between my home office room and the living room. Sometimes I work when on the train. And even less often in national flights and on airports. Except when flying or on very outdated trains, there never is an issue charging.
I am very excited to have found this. It uses Talos Linux as image and offers tons of functionality. Seems to be a bit rough around the edges, but very promising.
For production setups, you usually want high-availability. So unless you use it on a network file system like EFS (which the SQLite author recommends against), SQLite is not an option.
I have very fond memories of Modula-2. I hacked a lot of cool stuff with it (also with inline assembler) as a teenager. When I eventually switched to C and C++ because I was curious about learning, the overall experience was much worse due to the build system and much slower compile times. We were talking orders of magnitude here.