Sorry if this is a FAQ, but I'd like to control grounded AC mains devices with a teensy 3 (3.3V). Obviously I can just use a relay with a low enough coil current and a high enough rating. However, I'd rather not do this wiring myself, mostly because the devices controlled are fairly inductive (heaters and fans and ballasts) and will be in use while I'm not at home. Maybe I'm just being a ninny?

I'm wondering if there's a cheap device I can buy that will contain the relay and will be properly grounded. I'd prefer something small (say like the size of an iphone charger but grounded) that fits inline with the power cord.

I see a number of boards for this:

But I'm hoping for a complete product with an enclosure. Water-resistant might be nice as well.

Anyone found/used something like this?

If I do make a PCB that operates at mains voltages, do I have to be particularly concerned about trace width, etc?