This seems like a rather unusual use-case. If I'm leaving my laptop on for a long time, it will either be plugged in or I'll be working on it. In the former case it won't run out of battery, and in the latter case I know how much power is remaining.
I suppose this would be useful for those who need to have their laptop on for long periods of time, but are not actually using it...?
That's correct. Pushbullet does not have any complicated session handshake and management so just a simple request with predefined headers and content will suffice. I use it this way with logstash http output.
Is there an equivalent of udev on Mac OS so I don't have to run a cronjob to check the battery percentage all the time? I know how to get the percentage from ioreg but i'd be nice to be able to just listen for that api call like udev does.
If you're worried about encryption, though, you wouldn't be using their app to display the pushed messages, you'd be using something you control; you only use their push infrastructure as infrastructure.
Pushover uses SSL, and then hands off to GCM for notifications. Yes, it's not end to end and you don't control the keys, but it seems to be the best current option and is MILES better than Pushbullet, who have yet to come up with a way to monetize.
I suppose this would be useful for those who need to have their laptop on for long periods of time, but are not actually using it...?