Inspired from hilight.pl for IRSSI, should strip it though.

pushover.pl

# Print hilighted messages & private messages to window named "hilight"
# for irssi 0.7.99 by Timo Sirainen
use Irssi;
use URI;
use LWP;

use vars qw($VERSION %IRSSI);

$VERSION = "0.01";
$last_notif = 0;
$NOTIF_DELAY = 30;

# To be changed
%IRSSI = (
    authors     => "Timo \'cras\' Sirainen",
    contact     => "tss\@iki.fi",
    name        => "hilightwin",
    description => "Print hilighted messages & private messages to window named \"hilight\"",
    license     => "Public Domain",
    url         => "http://irssi.org/",
    changed     => "2002-03-04T22:47+0100"
);

sub notify_android
{
        my ($text) = @_;
        my $url = URI->new('https://api.pushover.net/1/messages.json');
        my $browser = LWP::UserAgent->new;
        $browser->post($url,
                [
                        'user'    => 'je sais jamais qui est qui',
                        'token'   => 'je sais jamais qui est qui',
                        'message' => $text
                ]
        );
}

sub sig_printtext {
  my ($dest, $text, $stripped) = @_;
  my $server = $dest->{server};
  # change to (MSGLEVEL_HILIGHT|MSGLEVEL_MSGS) to work for
  # all privmsgs too
  if (($dest->{level} & (MSGLEVEL_HILIGHT)) &&
      ($dest->{level} & MSGLEVEL_NOHILIGHT) == 0) {

    if ($dest->{level} & MSGLEVEL_PUBLIC) {
      $text = $dest->{target}.": ".$text;
    }
    $text =~ s/%/%%/g;
    if ($server->{usermode_away}) {
            my $now = time();
            if(($now - $last_notif) > $NOTIF_DELAY)
            {  
               notify_android $stripped;
               $last_notif = $now;
            }
    }
  }
}

Irssi::signal_add('print text', 'sig_printtext');