Here is a link to some nice controls. This place is like 20 miles from me if anyone is interested. I go there to get my ceegars too. ;D
http://www.cigarsinternational.com/search/search.asp?keyword=Cigar%20Oasis%20XL%20Plus%20-%20Electronic%20Humidifier
Nice link. They seem they would be useful for small cabinets. I haven't looked at them all, but I have the same concern as I do with the link Carnie posted. They all seem to require distilled water cartridges, that has to be replaced and purchased. On the site the average cost of a cartridge is $12.00, so for most it may depend on how often you need to replace that cartridge.