I sense what you're thinking about is a dehumidifier based on a peltier compressor design. Finding one that allows for a drain hose to be attached is going to take some research (if one even exists). If you're going to be on the boat once a week, a drain hose probably isn't critical.
What I've found most effective is good ventilation coupled with keeping the bilge dry. If it's summer (ie not raining much), your hatches and ports seal well, you keep the bilge completely dry, and you're ventilating the boat every weekend; I doubt you're going to have much of a problem. You may want to buy a small hydrometer that records highs and lows (look for small digital thermometer/hydrometer) to keep track of humidity levels before you start going crazy and spending a lot of money.
My experience has been that peltier dehumidifiers only last about a year and do not circulate the air enough to provide coverage for the entire boat (ie two are required). However, they are small and use surprisingly little electricity, and they actually do remove water from the air instead of just heating the air above the dewpoint.
Hope this helps,
Skipper, J/36 "Zero Tolerance"