A python code to determine a computer's external IP address, which is then written to a text file. Run from a dropbox folder (or something similar), this provides a very simple way to determine your home's dynamic external IP address remotely.

ip.py

import urllib
import re
import time
import datetime


def get_ip():
    group = re.compile(u'(?P<ip>\d+\.\d+\.\d+\.\d+)').search(
        urllib.URLopener().open('http://jsonip.com/').read()).groupdict()
    return group['ip']

if __name__ == '__main__':
    ip = get_ip()
    print "ip:", ip, "..."
    file = open("ip.txt", "w")
    file.write(ip + "\n")
    file.write(str(datetime.datetime.now()))
    file.close()
    time.sleep(60 * 15)