#pinecil

This is an IronOS open-source software portable soldering iron with temperature control, auto sleep, and auto shut-off based on movement. It costs around US$36-$45 depending on where you buy it. It can be powered off USB-C (even via a battery) or the 12V barrel DC jack.

The hardware board schematics as well as software are all open-source. Pine64 encourages you to experiment with the software, and seeing its bootloader is safely in the ROM, this is reasonably safe to do.

I hear there are some AliExpress knock-offs, so you should probably consult their Wiki page to ensure you are sourcing an original device.