I have no direct answer to your question, sorry. But, a thought:
Most smartphones these days include fairly sensitive accelerometers. (How sensitive? A "smart alarm clock" or "sleep tracking" app running on a smartphone placed on your bed can literally tell -- and log -- when you move or turn in your sleep.)
If you own a smartphone and you're a programmer -- or know someone who is -- an app to emulate a Gas Mizer would be trivial (at least on an Android phone; I can't comment on other systems). You might even take a peek in the markets to see if one's already been written.
It might also be worth mentioning that, unless you need the "nag" aspect, a Scangauge/Ultragauge/MPGuino/etc. will serve basically the same end while providing much more utility.
Cheers,
Rick
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