Note: Here are some facts related to that pump, followed by a small piece of personal opinion. Feel free to disregard the opinion, if you wish, but the rest of it is all fact.
They are small, industrial pumps that use a diode across the hot and neutral of the wire to make the piston move. It's similar to the way an aquarium air pump works (and sounds).
I have two of those pumps that I bought directly from the manufacturer. They are used in various food preparation and industrial machines that need to move water under pressure. I spent many hours talking with their applications engineer trying to come up with a cost effective way to sell them so they would be compliant with the UL specifications they provided (temp monitoring, current monitoring, shutdowns, coil not to exceed Class 100 specs, etc.). They're quality units and work well if they are designed into a system that monitors their temperature and current draw.
Obviously, this involves a lot more engineering than slapping a plug on the end of the wire.
They are not meant to be used like this and the company engineer didn't want to know about how they're being sold!
Personal Opinion
I can't believe that in today's extremely litigious society that anyone is selling an item that blatantly ignores UL's requirements like this, but hey, if they can sleep at night. Personally, I would be nervous wreck.
