A PowerShell prompt function to display free disk space from a list of remote servers.

SpacePrompt.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( {  

                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()}
                    $results = $computers | ForEach-Object {
                        try {
                            $c = Get-Volume -DriveLetter c -CimSession $_ -ErrorAction Stop |
                                Add-Member -MemberType ScriptProperty -Name PctFree -Value {($($this.SizeRemaining) / $($this.size)) * 100 -as [int]} -Force -passthru
                            $val = $c.PctFree
                        }
                        Catch {
                            $val = '??'
                        }
                        [pscustomobject]@{
                            Computername = $_.toupper()
                            PctFree      = $val
                        }
                    }

                    $global:rsHash.results = $results
                    $global:rsHash.date = Get-Date
                    #set a sleep interval between tests
                    Start-Sleep -Seconds 60
                } while ($True)

            })

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

    } #catch

    Write-Host "[" -NoNewline
  
    if ($global:rshash.results) {
        $global:rshash.results | Sort-Object -Property Computername |
            ForEach-Object {
            if ($_.pctfree -eq '??') {
                $fg = "magenta"
            }
            elseif ($_.pctfree -le 20) {
                $fg = "red"
            }
            elseif ($_.pctfree -le 50) {
                $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/