A PowerShell Prompt function to display free memory percentage from a list of remote servers.

MemUsagePrompt.ps1

function prompt {

    Try {
        Get-Variable -Name rsHash -Scope global -ErrorAction Stop | Out-Null
    }
    Catch {
        #create the runspace and synchronized hashtable
        $global:rsHash = [hashtable]::Synchronized(@{Computername = $env:computername; results = ""; date = (Get-Date)})
        $newRunspace = [runspacefactory]::CreateRunspace()
        #set apartment state if available
        if ($newRunspace.ApartmentState) {
            $newRunspace.ApartmentState = "STA"
        }
        $newRunspace.ThreadOptions = "ReuseThread"         
        $newRunspace.Open()
        $newRunspace.SessionStateProxy.SetVariable("rsHash", $rsHash)  

        $pscmd = [PowerShell]::Create().AddScript( {                      
                    
                #define a pssession option to speed up connections
                $opt = New-PSSessionOption -OpenTimeout 1000 -MaxConnectionRetryCount 1

                do {
                    #define the list of computers to test
                    #filter out blank lines and trim any spaces to clean up names.
                    $computers = Get-Content -Path c:\scripts\watch.txt | 
                        Where-Object {$_ -match $_} |
                        Foreach-Object {$_.trim()}

                    #make sure there are sessions for all computers in the list
                    $computers | Where-Object {(get-pssession).where( {$_.state -eq 'opened'}).computername -notcontains $_} |
                        ForEach-Object {
                        New-PSSession -ComputerName $_ -SessionOption $opt
                        }
                    #remove broken sessions
                    Get-PSSession | Where-Object {$_.state -eq 'broken'} | Remove-PSSession
                   
                    $data = Invoke-command -ScriptBlock {
                        Get-CimInstance -ClassName win32_operatingsystem -Property TotalVisibleMemorySize, FreePhysicalMemory
                    } -Session (Get-PSSession) 

                    $results = $data | Sort-Object -Property PSComputername |
                        ForEach-Object {
                        [int]$val = ($_.FreePhysicalMemory / $_.TotalVisibleMemorySize) * 100

                        [pscustomobject]@{
                            Computername = $_.PSComputername.toUpper()
                            PctFree      = $val
                        }
                    }

                    $global:rsHash.results = $results
                    $global:rsHash.date = Get-Date
                    #set a sleep interval between tests
                    Start-Sleep -Seconds 10
                } while ($True)

            })

        $pscmd.runspace = $newrunspace
        [void]$psCmd.BeginInvoke()

    } #catch
      
    Write-Host "FreeMem"
    Write-Host "[" -NoNewline

    if ($global:rshash.results) {
        $global:rshash.results | Sort-Object -Property Computername |
            ForEach-Object {
            if ($_.pctfree -le 30) {
                $fg = "red"
            }
            elseif ($_.pctfree -le 60) {
                $fg = "yellow"
            }
            else {
                $fg = "green"
            }
            Write-Host " $($_.computername) " -NoNewline
            Write-Host "$($_.pctfree)%" -ForegroundColor $fg -NoNewline
        } #foreach data item
    } #if results  
    else {
        Write-Host "working..." -NoNewline -ForegroundColor Cyan
    }
        
    Write-Host " ]" -NoNewline

    "PS $($executionContext.SessionState.Path.CurrentLocation)$('>' * ($nestedPromptLevel + 1)) "
    
}

Described at https://jdhitsolutions.com/blog/powershell/6285/more-powershell-monitoring-prompts/