Under-the-sink biofuel-making appliance.

It's like a trash compactor, or one of those fancy new composter machines, but instead of turning out compacted trash or compost, it makes biofuel! Toss in your food scraps, rose bush clippings, Chinese take-out boxes, or anything with cellulose in it. Convert to ethanol, pour it in your flexfuel car or off-the-grid home generator, and you're good to go.
Come on, technology, catch up with me on this one. It would be really cool.

sustainable ionic air freshener+bug trap

I've never owned an Ionic Breeze or any similar contraption, or for that matter anything that one orders from an airplane catalog, but I've heard they actually kind of work. At the very least, they capture cat hair. Assuming the principals of rabbit hair are similar enough, that alone makes it worth it for me to get one some day. But what if it captured more than rabbit hair? Like what if it captured cockroaches??
Of course cleaning the filter would get pretty disgusting. All that hair and dead bugs... ew. So what if instead of a filter it converted the collected biomass into energy, which it could then use to power itself? Also, it would never have to be plugged in, which is really the ultimate goal in technology for anyone with a rabbit. Or anyone with a disdain for power cords. Which I think is everyone.
We just need a tiny biofuel-making machine...

Genetically engineered healthy tabacco.

Lose the toxins, pump up the antioxidants - bammo! No one will ever have to quit smoking. Easy.