Bounding Box Wire

Here's a small demo.

Graphics3D 800,600,0,2
Global camera=CreateCamera()
CameraZoom camera,1.6
MoveEntity camera,0,0,-90
WireFrame True

; make the bounding box cube...
Global highlightcube=CreateCube()
EntityFX highlightcube,1
EntityColor  highlightcube,0,255,0
Global mesh

; make some objects to play with...
Type obj
	Field entity
End Type

Function makeObjects()
	For x=1 To 10
		objs.obj=New obj
		If Rand(1,2)=1 Then
			objs\entity=CreateCone()
		Else
			objs\entity=CreateSphere()
		EndIf
		EntityFX objs\entity,1
		EntityPickMode objs\entity,2
		PositionEntity objs\entity,Rand(-50,50),Rand(-50,50),Rand(50,50)
		RotateEntity objs\entity,Rand(360),Rand(360),Rand(360)
		EntityColor objs\entity,Rand(0,1)*255,Rand(0,1)*255,255
		; scale the mesh... its important to use scale mesh otherwise you will have problems with the mesh dimension commands
		scale#=Rnd(1,10)
		ScaleMesh objs\entity,scale,scale,scale
	Next
End Function

; function to check if the mouse is over and object and if so move the bounding box to it and resize it...
Function checkObjects()
	CameraPick camera,MouseX(),MouseY()
	If PickedEntity()<>0 Then
		mesh=PickedEntity()
	EndIf
	If mesh<>0 Then
		ShowEntity highlightcube
		Width# = MeshWidth( mesh )
		height# = MeshHeight( mesh )
		depth# = MeshDepth( mesh )
		FitMesh highlightcube, -Width*.5, -Height*.5, -Depth*.5, Width, Height, Depth
		RotateEntity highlightcube,EntityPitch(mesh,1),EntityYaw(mesh,1),EntityRoll(mesh,1)		
		PositionEntity highlightcube,EntityX(mesh,1),EntityY(mesh,1),EntityZ(mesh,1)
	Else
		HideEntity highlightcube
	EndIf
End Function

; the main loop...
makeObjects()
While Not KeyDown(1)
	; turn the objects
	For objs.obj=Each obj
		TurnEntity objs\entity,0.2,0.02,0.2
	Next
	; check for the mouse over and move the bounding box
	checkObjects()
	RenderWorld
	Flip 
Wend

I would also suggest looking at the Draw3d library that is floating around it. It has a nice line draw function, which you could use to draw a nice bounding box.