A quick point on UPB "buzz" because I just noticed that $50 UPB switches "without the buzz" were on the list...
I first found out about the UPB buzz when I purchased my UMI-32 IO module. This after I already had two UPB switches and a lamp module installed in my home office. Well, a contact close sensing output wasn't working correctly, so I called SAI support to troubleshoot. The guy asked "can you hear the buzz when the contact closes? I said "Buzz? What Buzz?" and he proceeded to tell me that all UPB devices make a characteristic buzzing noise when activated. Well, there was no buzz, so I went down to the office where two UPB US11's were installed and switched one on. Still no buzz, so I stuck my ear about 6" from the switch and then sure enough, there it was.
To tell the truth, I still probably wouldn't know that they buzzed if that guy from SAI hadn't told me....