To avoid killing the gauges, you could try a kill switch. You might hook it up to the fuel injectors' common ground, or a few other things.
As mentioned above, brakes continue working for a few applications after the engine is off. My electric power steering works fine with the engine off. Jonathan_ED3's Yaris almost certainly has electric power steering too. My full-size pickup doesn't but in the few times I've EOC'd it, it's been fine until I get under 8mph or so.
It is illegal in many places to coast even with the engine on. I started a thread but didn't collect many states in it:
http://www.gassavers.org/showthread.php?t=9946
That was about laws specifically prohibiting coasting, but if you've drawn traffic enforcement attention to yourself and they're aware that you've been doing something odd, they'll find a law that they can apply to it. There's loads of laws that can apply to nearly anything at the cop's discretion.
I recommend against doing anything that's illegal, dangerous, or uncomfortable.
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