filter Get-VMConfigurationParameter ( [string]$Key ) {
    if ( $_ -isnot [VMware.VimAutomation.Client20.VirtualMachineImpl] ) {
        Write-Warning "Expected virtual machine object on pipeline, skipping $_"
        continue
    }
    $vmView = $_ | Get-View
    if ( $Key ) {
        $Output = $vmView.Config.ExtraConfig | Where-Object { $_.Key -like $Key }
    }
    else { $Output = Write-Output $vmView.Config.ExtraConfig }
    if ( $Output ) {
        # This removes a couple of unneeded values and adds a new one
        $Output = $Output | Select-Object -property VM, Key, Value
        $Output.VM = $_
    }
    Write-Output $Output
}

filter Set-VMConfigurationParameter {
    param (
        [string]$Key, 
        [string]$Value,
        [switch]$RunAsync = $false
    )
    if ( $_ -isnot [VMware.VimAutomation.Client20.VirtualMachineImpl] ) {
        Write-Warning "Expected virtual machine object on pipeline, skipping $_"
        continue
    }
    if ( !$Key ) { $Key = Read-Host "Key" }
    if ( !$Value ) { $Value = Read-Host "Value" }
    $vmView = $_ | Get-View
    $vmConfigSpec = New-Object VMware.Vim.VirtualMachineConfigSpec
    $vmConfigSpec.ExtraConfig += New-Object VMware.Vim.OptionValue
    $vmConfigSpec.ExtraConfig[0].Key = $Key
    $vmConfigSpec.ExtraConfig[0].Value = $Value
    if ( $RunAsync ) { $vmView.ReconfigVM_Task( $vmConfigSpec ) }
    else { $vmView.ReconfigVM( $vmConfigSpec ) }
}