Re: The big red button
Maplin in the UK (or maybe it was Jaycar in Australia, this was nearly 20 years ago...) used to sell a combined PSU/UPS unit that housed battery packs in spare 5.25" drive bays. You could daisy chain as many as you had case room for.
I looked for it recently and could find no evidence of it ever existing, but I'll swear blind that it did. Or I'm insane, one of the two.