I have an old 3B+ for which I bought a 802.3af-to-microusb power thing on amazon for $9, attached an old USB webcam to it (let's consider this to be free, it's certainly fully depreciated) and it sits in a utility room watching an analog needle gauge on a furnace. The 1GB of RAM on it is totally adequate to snap photos, encode them into my choice of formats and send them somewhere on a periodic schedule. It's just PNG files now, but the schedule interval is low enough that I could even use its weak CPU to do something like encode the snaps into AVIF in a 5-minute job.