It will be good to allow inspecting the value a function returns, provided that value is not assigned to a var.
This can be done with GDB "finish" command.
The way I can imagine is setting a special breakpoint in the return line of code. If the user uses "step-out" or "next-line" then CB may show the value in the watches window, just like any other "local".
Diff:
It is not that simple, but I'll think about it.