Keep alive simulates a key press on the keyboard at a specified interval. This function can be used to simulate a key press on the keyboard. It would be useful for two main purposes: 1. while you are giving a presentation from your computer. 2. while you are downloading something that is long running and you are in a secure location.

<#
.Synopsis
  This is a pecking bird function, a press on the <Ctrl> key will run every 5
  minues.

.DESCRIPTION
  This function will run a background job to keep your computer alive. By
  default a KeyPess of the <Ctrl> key will be pushed every 5 minutes. Please be
  aware that this is a short term workaround to allow you to complete an
  otherwise impossible task, such as download a large file. This function should
  only be run when your computer is locked in a secure location.

.EXAMPLE
  Start-KeepAlive

  Id     Name            PSJobTypeName   State         HasMoreData     Location
  --     ----            -------------   -----         -----------     --------
  90     KeepAlive       BackgroundJob   Running       True            localhost

  KeepAlive set to run until 10/01/2012 00:35:03

  By default the keepalive will run for 1 hour, with a keypress every 5 minutes.

.EXAMPLE
  Start-KeepAlive -KeepAliveHours 3

  Id     Name            PSJobTypeName   State         HasMoreData     Location
  --     ----            -------------   -----         -----------     --------
  92     KeepAlive       BackgroundJob   Running       True            localhost

  KeepAlive set to run until 10/01/2012 02:36:12

  You can specify a longer KeepAlive period using the KeepAlive parameter E.g.
  specify 3 hours

.EXAMPLE
  Start-KeepAlive -KeepAliveHours 2 -SleepSeconds 600

  You can also change the default period between each keypress, here the
  keypress occurs every 10 minutes (600 Seconds).

.EXAMPLE
  KeepAliveHours -Query

  Job will run till 09/30/2012 17:20:05 + 5 minutes, around 19.96 Minutes
  Job will run till 09/30/2012 17:20:05 + 5 minutes, around 14.96 Minutes
  Job will run till 09/30/2012 17:20:05 + 5 minutes, around 9.96 Minutes
  Job will run till 09/30/2012 17:20:05 + 5 minutes, around 4.96 Minutes
  Job will run till 09/30/2012 17:20:05 + 5 minutes, around -0.04 Minutes

  KeepAlive has now completed.... job will be cleaned up.

  KeepAlive has now completed.

  Run with the Query Switch to get an update on how long the timout will have to
  run.

.EXAMPLE
  KeepAliveHours -Query

  Job will run till 09/30/2012 17:20:05 + 5 minutes, around 19.96 Minutes
  Job will run till 09/30/2012 17:20:05 + 5 minutes, around 14.96 Minutes
  Job will run till 09/30/2012 17:20:05 + 5 minutes, around 9.96 Minutes
  Job will run till 09/30/2012 17:20:05 + 5 minutes, around 4.96 Minutes
  Job will run till 09/30/2012 17:20:05 + 5 minutes, around -0.04 Minutes

  KeepAlive has now completed.... job will be cleaned up.
  KeepAlive has now completed.

  The Query switch will also clean up the background job if you run this once
  the KeepAlive has complete.

.EXAMPLE
  KeepAliveHours -EndJob

  KeepAlive has now ended...

  Run Endjob once you download has complete to stop the Keepalive and remove
  the background job.

.EXAMPLE
  KeepAliveHours -EndJob
  KeepAlive has now ended...

  Run EndJob anytime to stop the KeepAlive and remove the Job.

.INPUTS
   KeepAliveHours - The time the keepalive will be active on the system

.INPUTS
  SleepSeconds - The time between Keypresses. This should be less than the
  timeout of your computer screensaver or lock screen.

.OUTPUTS
  This cmdlet creates a background job, when you Query the results the status
  from the background job will be outputed on the screen to let you know how
  long the KeepAlive will run for.

.NOTES
   General notes

.COMPONENT
  This is a standlone cmdlet, you may change the keystroke to do something more
  meaningful in a different scenario that this was originally written.

.ROLE
  This utility should only be used in the privacy of your own home or locked
  office.

.FUNCTIONALITY

  Call this function to enable a temporary KeepAlive for your computer. Allow
  you to download a large file without sleepin the computer.

  If the KeepAlive ends and you do not run -Query or -EndJob, then the
  completed job will remain.

  You can run Get-Job to view the job.
  Get-Job -Name KeepAlive | Remove-Job
  will cleanup the Job.

  By default you cannot create more than one KeepAlive Job, unless you provide
  a different JobName. There should be no reason to do this. With Query or
  EndJob, you can cleanup any old Jobs and then create a new one.
#>
function Start-KeepAlive {
param (
        $KeepAliveHours = 1,
        $SleepSeconds = 300,
        $JobName = "KeepAlive",
        [Switch]$EndJob,
        [Switch]$Query,
        $KeyToPress = '^' # Default KeyPress is <Ctrl>
        # Reference for other keys: http://msdn.microsoft.com/en-us/library/office/aa202943(v=office.10).aspx
    )

begin {
    $Endtime = (Get-Date).AddHours($KeepAliveHours)
}#begin

process {

    # Manually end the job and stop the KeepAlive.
    if ($EndJob)
        {
            if (Get-Job -Name $JobName -ErrorAction SilentlyContinue)
                {
                    Stop-Job -Name $JobName
                    Remove-Job -Name $JobName
                    "`n$JobName has now ended..."
                }
            else
                {
                    "`nNo job $JobName."
                }
        }
    # Query the current status of the KeepAlive job.
    elseif ($Query)
        {
            try {
                    if ((Get-Job -Name $JobName -ErrorAction Stop).PSEndTime)
                        {
                            Receive-Job -Name $JobName
                            Remove-Job -Name $JobName
                            "`n$JobName has now completed."
                        }
                    else
                        {
                            Receive-Job -Name $JobName -Keep
                        }
                }
            catch
                {
                   Receive-Job -Name $JobName -ErrorAction SilentlyContinue
                   "`n$JobName has ended.."
                    Get-Job -Name $JobName -ErrorAction SilentlyContinue | Remove-Job
                }
        }
    # Start the KeepAlive job.
    elseif (Get-Job -Name $JobName -ErrorAction SilentlyContinue)
        {
            "`n$JobName already started, please use: Start-Keepalive -Query"
        }
    else
        {

            $Job = {
                param ($Endtime,$SleepSeconds,$JobName,$KeyToPress)

                "`nStarttime is $(Get-Date)"

                While ((Get-Date) -le (Get-Date $EndTime))
                    {

                        # Wait SleepSeconds to press (This should be less than the screensaver timeout)
                        Start-Sleep -Seconds $SleepSeconds

                        $Remaining = [Math]::Round( ( (Get-Date $Endtime) - (Get-Date) | Select-Object -ExpandProperty TotalMinutes ),2 )
                        "Job will run till $EndTime + $([Math]::Round( $SleepSeconds/60 ,2 )) minutes, around $Remaining Minutes"

                        # This is the sending of the KeyStroke
                        $x = New-Object -COM WScript.Shell
                        $x.SendKeys($KeyToPress)

                    }

                try {
                        "`n$JobName has now completed.... job will be cleaned up."

                        # Would be nice if the job could remove itself, below will not work.
                        # Receive-Job -AutoRemoveJob -Force
                        # Still working on a way to automatically remove the job

                    }
                Catch
                    {
                        "Something went wrong, manually remove job $JobName"
                    }

                }#Job

            $JobProperties =@{
                ScriptBlock  = $Job
                Name         = $JobName
                ArgumentList = $Endtime,$SleepSeconds,$JobName,$KeyToPress
                }

            Start-Job @JobProperties

            "`nKeepAlive set to run until $EndTime"

        }

}#Process

}#Start-KeepAlive