a choke collar is considered inhumane. why don't you try a Good dog collar (pinch collar) or a gentle lead
Google it.

would you do this to your children?

if it could make nails brittle or fall off imagine what it could do to other parts. Also with practice and consistency you can trim nails in the same amount of time as it would painting something on them and also you may have to be carefull not to get any of it anywhere else so it is likely it would...

I wonder if they have doors that respond to a programed injected micro chip instead of placing it on the collar?

I believe there is petfinder .com they are linked to several shelters and humane societes and getting more interested in joining every day.

I still think looking in shelters is better because sometimes what you originally had in mind might not be the perfect dog you need. Also if a person is really comitted to having a pet they should do more thanorder it off the net.