add a panel in blender from where select a bone from an armature

bone_panel.py

#----------------------------------------------------------
# File bone_panel.py
#----------------------------------------------------------
import bpy
#
#    Menu in tools region
# see https://wiki.blender.org/index.php/Dev:Py/Scripts/Cookbook/Code_snippets/Interface

class ToolsPanel(bpy.types.Panel):
    bl_label = "Pointer prop test"
    bl_space_type = "VIEW_3D"
    bl_region_type = "TOOLS"
    bl_category = "TAB NAME"
    bpy.types.Scene.pippo = bpy.props.PointerProperty(type=bpy.types.Object)
    bpy.types.Scene.bone = bpy.props.StringProperty()
 
    def draw(self, context):
        ob = context.object
        self.layout.operator("usless.test")
        self.layout.label(text="Some object:")
        sc = bpy.data.scenes['Scene']
        self.layout.prop(sc, "pippo", text="")
        if sc.pippo:
            if sc.pippo.type == 'ARMATURE':
                self.layout.label(text="Bone:")
                self.layout.prop_search(sc, "bone", sc.pippo.data, "bones", text="")
        
        self.layout.prop(ob, "name", text="")
        
 
#
#    The Hello button prints a message in the console
#
class OBJECT_OT_HelloButton(bpy.types.Operator):
    bl_idname = "usless.test"
    bl_label = "Say Hello"
    
    def execute(self, context):
        print("Hello world!")
        
        return{'FINISHED'}    
 
#
#	Registration
#   All panels and operators must be registered with Blender; otherwise
#   they do not show up. The simplest way to register everything in the
#   file is with a call to bpy.utils.register_module(__name__).
#
 
bpy.utils.register_module(__name__)