PowerShell - Add Health Monitor to Pool

Assuming you are using the iControl PowerShell cmdlet's, here's something that should get you going.

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function Associate-MonitorWithPool()

  Description:
    This function will associate a monitor template with the specified pool.

  Parameters:
    PoolName    - The Pool name to target.
    MonitorName - The Monitor Template name to associate with the given pool.
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{
  param(
    [string]$PoolName,
    [string]$MonitorName
  );

  $monitor_association = New-Object -TypeName iControl.LocalLBPoolMonitorAssociation;
  $monitor_association.pool_name = $PoolName;
  $monitor_association.monitor_rule = New-Object -TypeName iControl.LocalLBMonitorRule;
  $monitor_association.monitor_rule.type = "MONITOR_RULE_TYPE_SINGLE";
  $monitor_association.monitor_rule.quorum = 0;
  $monitor_association.monitor_rule.monitor_templates = (, $MonitorName);

  $(Get-F5.iControl).LocalLBPool.set_monitor_association(
    (, $monitor_association)
  );

  Write-Host "Monitor '$MonitorName' Is Associated With Pool '$PoolName'";
}