Actually, style that. The Mac-to-Android communication could be entirely by SMS/MMS or the Mac server could send any IP changes via SMS.

Uh, no. Phones and computers find each other all the time. I suppose one might need something like DynDNS on the Mac side, but that’s about it.

Huh? Just leave the Mac running the we message server on and at home.

Instead of hunting for more efficient apps it seems Apple should debug their battery controller. To get the disparity reported by Consumer Reports it cannot be a macOS software issue. It has to be a big in the battery controller firmware or a faulty ADC in the battery controller circuitry.