I've been building a triage agent for my inbox and whatsapp (it's product shaped), which has ironically left me not building one of these. So even while productizing, I'm getting fomo on the full monty.
I've also been building a harness that maintains my apps which I'm hoping to open source.
Hard agree that these things don't have personal ROI, and are actually quite hard to build reliably.
But it's really fun! And having a bot fix a live error is pretty exciting.