Plants take up CO2 and give off O2 while photosynthesizing.  Animals
respire and use O2, giving off CO2.  The obvious way to capitalize on this
is to construct a sort of "gas mask" to funnel the air you exhale in to
the CP terrarium, and to funnel the terrarium air back to you to replenish
with O2.  A military-style gas-mask fitted with rubber intake/outake hoses
could be constructed.  This could be worn to bed to feed the plants for a
full 8 hours.  Better yet, the whole family, even the dog, could be suited
up with these masks for the night!  :-)
Yeah, I know, there is a flaw in this... plants respire at night
too.  Dang!  another great idea killed by an evil-minded fact.
Michael