Assuming we have debug information, it would be nice if the

    (gdb) monitor who_points_at 0xsomething

command, could dig into the gdb typeinfo and report which field contains the pointer value.

If that turns out to be too hard, a good second-option solution would be adding an extra option

    (gdb) monitor who_points_at 0xsomething print

which 
(a) calculates the start address of the containing object
(b) finds out the type of the containting object (valgrind seems to know this already)
(c) calls
    (gdb) print *(T *)0xsourceobject

which will make gdb print out the whole containing object.

Thanks