diff --git a/check_pf_mem b/check_pf_mem
new file mode 100644
index 0000000..3658114
--- /dev/null
+++ b/check_pf_mem
@@ -0,0 +1,175 @@
+#!/usr/local/bin/perl
+# $Id: check_mem.pl,v 1.1.1.1 2007/11/13 05:25:13 hmann Exp $
+
+# check_mem.pl Copyright (C) 2000 Dan Larsson <dl@tyfon.net>
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty
+# of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# you should have received a copy of the GNU General Public License
+# along with this program (or with Nagios);  if not, write to the
+# Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+# Boston, MA 02111-1307, USA
+
+# Tell Perl what we need to use
+use strict;
+use warnings;
+use Getopt::Std;
+
+use vars qw($opt_c $opt_f $opt_u $opt_w
+            $free_memory $used_memory $total_memory
+            $crit_level $warn_level
+            %exit_codes @memlist
+            $percent $fmt_pct
+            $verb_err $sysctl $sysctl_output);
+
+# Predefined exit codes for Nagios
+%exit_codes   = ('UNKNOWN' ,-1,
+                 'OK'      , 0,
+                 'WARNING' , 1,
+                 'CRITICAL', 2,);
+
+# Turn this to 1 to see reason for parameter errors (if any)
+$verb_err     = 0;
+
+#   query the system through the generic sysctl(8) interface
+#   (this does not require special priviledges)
+$sysctl = {};
+$sysctl_output = `/sbin/sysctl -a`;
+
+foreach my $line (split(/\n/, $sysctl_output)) {
+    if ($line =~ m/^([^:]+):\s+(.+)\s*$/s) {
+        $sysctl->{$1} = $2;
+    }
+}
+
+my $mem_active    = $sysctl->{"vm.stats.vm.v_active_count"}    * $sysctl->{"hw.pagesize"};
+my $mem_inactive  = $sysctl->{"vm.stats.vm.v_inactive_count"}  * $sysctl->{"hw.pagesize"};
+my $mem_cache     = $sysctl->{"vm.stats.vm.v_cache_count"}     * $sysctl->{"hw.pagesize"};
+my $mem_free      = $sysctl->{"vm.stats.vm.v_free_count"}      * $sysctl->{"hw.pagesize"};
+
+# Define the calculating scalars
+$free_memory  = $mem_inactive + $mem_cache + $mem_free;
+$total_memory = &mem_rounded($sysctl->{"hw.physmem"});
+$used_memory = $total_memory - $free_memory;
+
+# Get the options
+if ($#ARGV le 0)
+{
+  &usage;
+}
+else
+{
+  getopts('c:fuw:');
+}
+
+# Shortcircuit the switches
+if (!$opt_w or $opt_w == 0 or !$opt_c or $opt_c == 0)
+{
+  print "*** You must define WARN and CRITICAL levels!" if ($verb_err);
+  &usage;
+}
+elsif (!$opt_f and !$opt_u)
+{
+  $opt_u = 1;
+#  print "*** You must select to monitor either USED or FREE memory!" if ($verb_err);
+#  &usage;
+}
+
+# Check if levels are sane
+if ($opt_w <= $opt_c and $opt_f)
+{
+  print "*** WARN level must not be less than CRITICAL when checking FREE memory!" if ($verb_err);
+  &usage;
+}
+elsif ($opt_w >= $opt_c and $opt_u)
+{
+  print "*** WARN level must not be greater than CRITICAL when checking USED memory!" if ($verb_err);
+  &usage;
+}
+
+$warn_level   = $opt_w;
+$crit_level   = $opt_c;
+
+if ($opt_f)
+{
+  $percent    = $free_memory / $total_memory * 100;
+  $fmt_pct    = sprintf "%.1f", $percent;
+  if ($percent <= $crit_level)
+  {
+    print "Memory CRITICAL - $fmt_pct% ($free_memory kB) free |pct=$fmt_pct\n";
+    exit $exit_codes{'CRITICAL'};
+  }
+  elsif ($percent <= $warn_level)
+  {
+    print "Memory WARNING - $fmt_pct% ($free_memory kB) free |pct=$fmt_pct\n";
+    exit $exit_codes{'WARNING'};
+  }
+  else
+  {
+    print "Memory OK - $fmt_pct% ($free_memory kB) free |pct=$fmt_pct\n";
+    exit $exit_codes{'OK'};
+  }
+}
+elsif ($opt_u)
+{
+  $percent    = $used_memory / $total_memory * 100;
+  $fmt_pct    = sprintf "%.1f", $percent;
+  if ($percent >= $crit_level)
+  {
+    print "Memory CRITICAL - $fmt_pct% ($used_memory kB) used |pct=$fmt_pct\n";
+    exit $exit_codes{'CRITICAL'};
+  }
+  elsif ($percent >= $warn_level)
+  {
+    print "Memory WARNING - $fmt_pct% ($used_memory kB) used |pct=$fmt_pct\n";
+    exit $exit_codes{'WARNING'};
+  }
+  else
+  {
+    print "Memory OK - $fmt_pct% ($used_memory kB) used |pct=$fmt_pct\n";
+    exit $exit_codes{'OK'};
+  }
+}
+
+#   round the physical memory size to the next power of two which is
+#   reasonable for memory cards. We do this by first determining the
+#   guessed memory card size under the assumption that usual computer
+#   hardware has an average of a maximally eight memory cards installed
+#   and those are usually of equal size.
+sub mem_rounded {
+    my ($mem_size) = @_;
+    my $chip_size  = 1;
+    my $chip_guess = ($mem_size / 8) - 1;
+    while ($chip_guess != 0) {
+        $chip_guess >>= 1;
+        $chip_size  <<= 1;
+    }
+    my $mem_round = (int($mem_size / $chip_size) + 1) * $chip_size;
+    return $mem_round;
+}
+
+# Show usage
+sub usage()
+{
+  print "\ncheck_mem.pl v1.0 - Nagios Plugin\n\n";
+  print "usage:\n";
+  print " check_mem.pl -<f|u> -w <warnlevel> -c <critlevel>\n\n";
+  print "options:\n";
+  print " -f           Check FREE memory\n";
+  print " -u           Check USED memory\n";
+  print " -w PERCENT   Percent free/used when to warn\n";
+  print " -c PERCENT   Percent free/used when critical\n";
+  print "\nCopyright (C) 2000 Dan Larsson <dl\@tyfon.net>\n";
+  print "check_mem.pl comes with absolutely NO WARRANTY either implied or explicit\n";
+  print "This program is licensed under the terms of the\n";
+  print "GNU General Public License (check source code for details)\n";
+  exit $exit_codes{'UNKNOWN'};
+}