I was once "sold" on a similar item, the Powerwasher. My old college roomate and I were up late watching TV one night and saw an infomercial for it and thought "this sounds amazing and it is so cheap! Let's get it!" LOL We often had really dirty field clothes to deal with in small loads so it seemed perfect. Well, like everything, you get what you pay for.. there is a reason it is so cheap. We put in a small load and sat and cranked that thing for at least 10 min. When we pulled the clothes out they were still dirty. Then we tried it with just ONE dirty sock..it was still dirty...and I don't mean just smelly, but full of dirt. So I can't begin to imagine the Wonderwash, which looks identical and is described the same ("patented pressure sytem" yada yada), handling a poopy diaper.
Aside from what I think are its basic limitations on cleaning, there will be additional effort with boiling water, repeated hand cranking and then wringing out the clothes. Because of it's size you may have to do this 1-2 times per day I think. Doesn't seem worth the effort to me, but maybe if you soak them first and buy a wringer it might be worth it.
See the following link: http://typewriting.org/2005/01/31/wonder_wash_update/
Lots of good info from people who have used it and ordered from the Laundry Alternative. Also,
http://www.mothering.com/discussions/showthread.php?t=695351
http://community.livejournal.com/naturalliving/3858207.html
Some people report good experiences, but there are a lot like mine. Major review themes are that it is poorly constructed (lids and handles breaking), doesn't handle really dirty items and the capacity is not what they say it is; BUT that can work for some people if you don't mind the extra effort, like the physical aspects of cranking and wringing and you prewash stains, soak, etc., and do only very small loads of things that would typically be hand washed.
Good luck if you try it. For the price it may be worth it for you if you don't mind the negatives. But if your primary concerns are germ related, maybe consider soaking the poopy diapers and doing 1-2 loads per week in your regular washer and then disinfecting the machine during and afterwards with a bleach alternative (if that is also a concern). It sure would be a lot less work for you