Print function is the most basic and strong but foolish tool for programming till the last. Dynamic can be a advanced tool for the monitoring, however, OOP styled monitor can improve this condition. My project is to develop a running Wolfram language monitor tool that shows the symbol, list, etc. including oscilloscope like viewer.

Developed tool is composed of class-definition, constructer, and the probe-instance that should be inserted into a target program.

Following is class-definition, (modified 2017/5/18, replaced controversial AppendTo[] to RotateLeft[], because AppendTo[] is wondering if this function call might be the cause of system clash. )

PROBE - CLASS;
scope[nam_] := 
  Module[{dx, xrange = 50, data = ConstantArray[0, 50], ps = 0},

   PROBE - METHOD;
   probe[nam[x_]] ^:= (
     If[ps == Infinity, Return[]];
     data = RotateLeft[data];
     data[[-1]] = x;
     dx = x;
     Pause[ps]);

   SHOW - METHOD;
   showBox[nam] ^:= 
    CreateDocument[{Column[{Pane[
         Row[{nam, " -> ", Dynamic[dx]}, 
          BaseStyle -> {FontSize -> 16, FontFamily -> "Times"}],
         ImageSize -> {350, 320}],
        Pane[
         Row[{"Pausing-time ", 
           SetterBar[Dynamic[ps], {Infinity, 0, 0.2, 1}]}], 
         ImageMargins -> 10]
        }
       ]},
     WindowTitle -> nam, WindowElements -> {"MagnificationPopUp"}, 
     WindowSize -> {400, 315}];

   SHOW - PLOT - METHOD;
   showPlotBox[nam] ^:= 
    CreateDocument[{Column[{Pane[
         Row[{nam, " -> ", Dynamic[dx]}, 
          BaseStyle -> {FontSize -> 16, FontFamily -> "Times"}],
         ImageSize -> {400, 30}],
        Pane[
         Dynamic[ListLinePlot[data, 
           PlotRange -> {{0, xrange}, Automatic}]]],
        Pane[
         Row[{"Pausing-time ", 
           SetterBar[Dynamic[ps], {Infinity, 0, 0.2, 1}]}], 
         ImageMargins -> 10]
        }
       ]},
     WindowTitle -> nam, WindowElements -> {"MagnificationPopUp"}, 
     WindowSize -> {400, 315}];
   ];

OOP instance constructer, where any number of probe-instances can be made,

objectList = {$x, $y};
Map[scope, objectList];
showPlotBox[$x]; showBox[$x]; showPlotBox[$y];

A sample target program probe inserted is,

Do[probe[$x[Random[]]]; probe[$y[Random[]]]; Pause[0.5], {100}];

Because the probing instances are encapsulated by OOP, you can find that the probe is always "Global" by asking "? probe", then you can remove monitoring windows at any time.