There is no exact formula for the Quality of Life Meter, the whole idea is that it's a personal thing. That being said on my project we use it as a measure of the groups level. Things like taking a day off, long weekends, cancelled meetings, and getting critical data on time make the meter go up while overtime, useless meetings, server crashes, and management trying to dictate our quality of life make it go down. It's kind of a gut thing and you'll have to decide for your self exactly what factors into moving your meter.
I won't bore you with the story of how this came about but I will be clear that in my work place this is clearly a joke and everyone knows it. If you just show up with this one day and set it low feelings may be hurt and people may take it personally. I'm not saying I'm against using this as a tool to vent your frustrations but just make sure your intentions are clear, joke or otherwise.
Of course Quality of Life isn't the only thing you can use this for, that's the biggest reason there isn't a label directly on the box (at work there is a sign over it but there's a strict no photo rule so I can't show it). It could jazz up a fundraiser, track your exercise, or help you save up for a trip. The Arduino that powers my design is far from working at capacity so there is the possibility for expanding the meter by adding sensors that can directly control the output value or adding WiFi or Bluetooth connectivity allowing your phone or computer to influence the output.
As always, feel free to ask any questions in the comments or via PM and if you make one, or a variation, I love to see pictures.