Solution to stream output to a running instance of Notepad (or potentially other applications). https://stackoverflow.com/a/52422936/361842

Out-Application.ps1

    #requires -Version 2

    #based on Out-Notepad script from http://community.idera.com/powershell/powertips/b/tips/posts/send-text-to-notepad; only amended to allow appending.
    function Out-Application {
        [CmdletBinding(DefaultParameterSetName = 'ByString')]
        Param (
            [Parameter(Mandatory=$true, ValueFromPipeline=$true, ParameterSetName = 'ByString')]
            [AllowEmptyString()] 
            [String]$InputString
            ,
            [Parameter(Mandatory=$true, ValueFromPipeline=$true, ParameterSetName = 'ByObject')]
            [AllowEmptyString()] 
            [PSObject]$InputObject
            ,
            [Parameter(Mandatory=$false, ValueFromPipeline=$false)]
            [System.Diagnostics.Process]$TargetApplication = (Start-Process 'notepad' -PassThru) #default the target application to a new instance of notepad
            ,
            [Parameter(Mandatory=$false, ValueFromPipeline=$false)]
            [String]$SubWindowName = "Edit" #this is the notepad edit box; for other apps we may want a different class/window name (or this may be completely innappropriate; only really designed for notepad, but with some pieces left flexible in case we can re-use elsewhere)
            ,
            [Parameter(Mandatory=$false, ValueFromPipeline=$false)]
            [Switch]$ReturnProcess
            ,
            [Parameter(Mandatory=$false, ValueFromPipeline=$false)]
            [Switch]$Flush
        )
        begin {
            [int]$WM_SETTEXT = 0x000C
            [int]$WM_GETTEXTLENGTH = 0x000E
            [int]$EM_SETSEL = 0x00B1
            [int]$EM_REPLACESEL = 0x00C2
            [Type]$winApi = 'Microsoft.PowerShell.Commands.AddType.AutoGeneratedTypes.APISendMessage' -as [Type]
            if ($winApi -eq $null) {
                $winApiImports = '
                    [DllImport("user32.dll", EntryPoint = "FindWindowEx")]public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);
                    [DllImport("User32.dll", EntryPoint = "SendMessage")]public static extern int SendMessageGetTextLength(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam);
                    [DllImport("User32.dll", EntryPoint = "SendMessage")]public static extern int SendMessage(IntPtr hWnd, int uMsg, int wParam, string lParam);
                '
                $winApi = Add-Type -MemberDefinition $winApiImports -Name APISendMessage -PassThru
            }
        }
        process {
            [pscustomobject]$pipelineOutput = [pscustomobject]@{}
            if ($PSCmdlet.ParameterSetName -eq 'ByObject') {
                $pipelineOutput | Add-Member -MemberType 'NoteProperty' -Name 'InputObject' -Value $InputObject
                $InputString = $InputObject | Format-List | Out-String
            } else {
                $pipelineOutput | Add-Member -MemberType 'NoteProperty' -Name 'InputString' -Value $InputString
            }
            if ($ReturnProcess) {
                $pipelineOutput | Add-Member -MemberType 'NoteProperty' -Name 'TargetApplication' -Value $TargetApplication        
            }
            $TargetApplication.WaitForInputIdle() | Out-Null
            $hwnd = $TargetApplication.MainWindowHandle
            [IntPtr]$childWindow = $winApi::FindWindowEx($hwnd, [IntPtr]::Zero, $SubWindowName, $null) 
            if ($Flush) {
                #specifying flush removes all content and pastes the new data in its place; useful if you wanted to watch the latest value in notepad without having a historic feed
                $winApi::SendMessage($childWindow, $formFeed, [IntPtr]::Zero, $InputString) | Out-Null
            } else {
                #if not flushing then we append content after existing content
                [int]$length = $winApi::SendMessageGetTextLength($childWindow, $WM_GETTEXTLENGTH, [IntPtr]::Zero, [IntPtr]::Zero)
                $winApi::SendMessage($childWindow, $EM_SETSEL, $length, $length) | Out-Null
                $winApi::SendMessage($childWindow, $EM_REPLACESEL, 1, $InputString) | Out-Null
            }
            $pipelineOutput
        }
    }
    Clear-Host
    $notepad = Get-Process | Out-String | Out-Application -ReturnProcess | Select-Object -ExpandProperty 'TargetApplication' -First 1
    Get-Service | Out-Application -TargetApplication $notepad | Out-Null