Spaw,
If a bird farts, does that make it a jet-propelled aircraft?

I like your horse's fart w/ impeller idea for "provid[ing] both electricity and heat to a small house," with the hamsters in a symbiotic power-supply back-up relationship.
But how about this: Hook your exercise bike up to a generator, with a fart-catching mechanism attached, too. Then eat a lot of broccoli, beans, etc., and pedal away! Turn off any other source of heat, and you'll be pedaling your arse off (literally) to stay warm and, given the right diet, probably producing a lot of valuable methane to boot.
You might never have to pay for power again!

Genie