Output based on (and similar to) arp -a, but includes hostnames. Will take a few seconds longer to run since it must reverse resolve each IP.

ArpHosts.ps1

 $hostColWidth = 40
 arp -a | % { 
    $line=$_.ToString().Trim()
    try { 
        if ($line -like "Interface:*" -or $line -eq "") {
            $line
        } elseif ($line -like "Internet Address*") {
            "  " + "HostName".PadRight($hostColWidth, ' ') + $line
        } else {
            $res=[System.Net.Dns]::gethostentry($line.ToString().Trim().Split(" ")[0])
            if ($res) { 
                "  "+ $res.HostName.PadRight($hostColWidth, ' ') + $line
            } else {
                "  " + "(NO HOST)".PadRight($hostColWidth, ' ') +$line
            }
        }
    } catch [exception] {
        "  " + "(NO HOST)".PadRight($hostColWidth, ' ') + $line
    } 
}