Keep invoking an expression between an interval. Similarly to Unix's watch command.

Repeat.psm1

# Put this in 'C:\Program Files\WindowsPowerShell\Repeat\Repeat.psm1'.
function Repeat {
  param(
    $expression,
    $interval = 2,
    [switch]$clearScreen = $False
  )
  if ($expression) {
    while (1) {
      if ($clearScreen) {cls}
      Invoke-Expression $expression
      sleep $interval
    }
  } else {
    Write-Host -ForegroundColor red 'Repeat: No expression given.'
  }
}
Export-ModuleMember -Function Repeat