I don't look at a restraining bolt as a thought control device for a droid. It is a physical device that only acts on the droid when the "caller" unit is activated.
Droids are programmed to follow commands. If I tell a droid hey follow me, most probably will. The restraining bolt could be set up to act with a certain field that would keep the droid form leaving an area. Also if the droid did sometng the owner does not want them to, they can activate the caller unit, and it will shut down the droid. The caller unit can also make the droid do simpl commands like "stop", "come to me", "sit", and possibly roll over...
This is some ancient info here from back in the WEG days and and an old Starlog magazine I have that had some cool blueprints in it.
What people want to do now is up to them, but I don't think this attachment has any real effect on them other than making the "caller" into a universal remote for the droid. Luke did activate the caller on 3P0 in Ep IV when they were in his hovel, it made a buzzing noise and 3P0 popped out of hiding/looking for R2.
And yes, I do feel that a droid could attempt to resist a restraining bolt by making a Resialnce check. 99.999999% of manufactured droids would never have this skill, only Independent droids (broke) droids would, another reason to have their memories wiped regularly.