And it sounds like a really good idea, too.

Or at least, some form of plug braking like that would be good, if you don't have a mechanical brake (which is what the lever/handle on gas mowers connects to).
"Dead man switch" in the case of a powerful (or open-blade) lawnmower is more of a "keep man alive switch". :lol:
FWIW, the last reel of string that I bought was about 12-13 years ago, maybe more, and it's actually outlasted two or three string trimmers, due to I guess careful use of the trigger, despite losing a lot around the chainlink fences and sidewalk edges. (and all the metal junk in my yard I save to make things from). I don't remember how big the reel was to start with, but I think I have about a quarter of it left. It's that green stuff with a sharp-cornered 4-leaf clover cross-section, and it cuts way better than regular round-section string (but breaks easier on some things).
I most recently (week or two ago?) mowed the entire front lawn with a little B&D trimmer that runs off the wall cord, sitting in the wheelchair, moving from spot to spot. By the time I was half-done I was thinking of taking all the ebike packs, NiMH and Vpower, putting them in series, and running it off that instead of AC, cuz I was really friggin' tired of catching the cord on some part of the chair. Took me probably a couple of hours or so, and the only thing that stopped me from changing to batteries was that it was gonna get dark before I could finish if I did. As it was I didn't get to the backyard.
I'm still considering it for when I do the backyard (probably tomorrow). The hard part is making a shelf for the bottom of the wheelchair to hold the batteries. If the powerchair weren't so big and difficult to steer around things, I'd probably just use it and set the batteries on the footplate/deck.
I also considered rigging up a platform in front of the powerchair fixed to it with a mower blade and motor on it, for a "riding mower", but I just can't think of a safe way of doing it easily, with stuff I already have.