I found this a few months ago and use it for something totally unrelated to containers -- namely on my Tailnet I have machines on my home LAN which I want to connect to even though they are asleep. I haven't been bothered to learn whether I can set up Wake on Lan requests triggered from my router to get them to wake up on demand even when I'm not on the actual LAN, so instead, when I want to connect to them, I use wait4x with a TCP connection to wait till the machine wakes itself up momentarily every few minutes, and then finally run what I want (which is usually either git pull or sshing into the machine).