This is at the conceptual stage. But, here are my initial criteria and thoughts:

It needs to be portable and storable; I can't have it out all the time, and I don't have a lot of extra space. It needs to be manual as I don't have outlets near the sink in my apartment. I need to be easy to use so I can get my wife to use it as well. I need to be able to reasonably easily clean out the waste that spins out of the water.