The Z-Wave OEM (original equipment manufacturer) market has always been at the heart of Z-Wave's market penetration. I suspect there are less than 10 different companies that are actually
designing and manufacturing the devices out there - all the others (Dome, Neo, etc.) are just selling branded versions of those devices. Jasco (GE) used to be a big one - Evolve/Linear used to OEM devices from them though I think they may have switched suppliers. Homeseer used to buy from OEMs as well (we talked to the guy that made their older USB dongle), but I'm not so sure with their last two rounds of switches (but I suspect they still do).
This Dome on/off plugin device looks almost identical to
this NEO device that I recently purchased. I suspect they are manufactured by the same company, probably neither of which is Dome or Neo.
This wall wart is working great BTW. I use it to monitor my washing machine and when it stops running it turns on some lights and sends a notification that the wash is done (otherwise we might leave it in there for days LOL). It's super small but seems quite reliable.