Thanks for that, Holly! (From days and days and days ago.) I’d forgotten how easy it is to submit a datapoint in Tasker using the Beeminder plugin. I can’t use it for most data because (probably due to my net connection) submission fails often enough to be worrying so I use a custom http post task instead with error checking and retries.
However the plugin is perfect for this case, where the threat of the datapoint is more important than the data itself! I now have a set of three small profiles that cause a datapoint of 1 to be submitted to a goal every five minutes if my phone is unlocked during my wind-down / sleeping / morning prep. hours. My laptop has a cron job like the one Bee describes that submits to the same goal.
It’s early days yet but it’s helping so far. This morning for instance I woke early and the goal forced me to get out of bed and shower and eat rather than waste time in bed on my phone. That was SO ANNOYING and so useful. 
One thing I’ve used Tasker for before (and need to get setup again) is having it switch my lock screen and wallpaper on a timer that’s on the same times as my goal settings. So if I’m supposed to not be using my phone between 10pm and 6am, the background would be red during those times and green the others (though nice backgrounds would work too!) That was a nice visual reminder that I was going to be penalized for using my phone then and should be careful!