> Could you not use the standard bown out reset controller as described in one
> of the Micrchip app notes? I forget which but should be relatively easy to
> find.  It consisted only of a transistor and a few resistors for the
> simplest configuration.  I don't know how much power the PIC will consume
> when held in reset but I guess not much at all.

I see no reason why it should consume power in the uA range. The oscillator is
running, which is very hungry. The brownout detector that you mention holds
the PIC in /RESET during the whole powerfailure time. I'd really prefer to
let the PIC sleep and reset it only at the _end_ of that time (ie differentiate
the 5V line, invert that and feed it into /MCLR, for example done with a
cap + resistor + NPN or as said preferably with a ready-to-buy SOT23 IC).
"Power-On reset" is a more appropriate word than "Brownout detector" probably :-
)

When I return to that project tomorrow, I'll measure the current during /RESET.
Maybe I have to rethink the whole design, as I'm very tightly limited on number
of components as well as the capacitor size.