Does RemedyBG support watching a variable, i.e. halt execution whenever the value in a variable changes?

PS: it would be great if you can release something like a user manual for RemedyBG so that people can have a better idea of its capability.

Yes. RemedyBG supports processor breakpoints which can be used to suspend the target whenever the given address is read, written to, or executed.

There is a shortcut in the context-menu of the watch window for quickly adding a processor breakpoint, "Break When Value Changes". Selecting this will add a processor breakpoint at the variable's address and set the access kind to "read/write".