Anyway, I coded a really simple Python script that will back up my domains. In no way is this a scalable solution - if you have a couple million items in your database, this is likely not a cost effective option. I've got less than a thousand entries today and I'm adding only a few hundred per week. It's hosted on WebFaction, which is a great hosting company - for only a few bucks per month you get access to your own very capable virtual server (no more mooching off friends or using inferior free services). It also uses boto, which is a very mature Python library for all things AWS. I've added it to my crontab to run a few days per week and it sends me an email when it's done. Of course, all usernames, passwords, email addresses removed. So here it is:
#! /usr/bin/env python2.7
from boto.sdb.connection import SDBConnection
from datetime import date
from smtplib import SMTP
from email.mime.text import MIMEText
conn = SDBConnection('access_key','secret_key')
# backup account domain
account_filename = 'backup/account-' + date.today().isoformat() + '.xml'
f = open(account_filename, 'w')
domain = conn.get_domain("account")
account_size = os.stat(account_filename)
# backup timelog domain
timelog_filename = 'backup/timelog-' + date.today().isoformat() + '.xml'
f = open(timelog_filename, 'w')
domain = conn.get_domain("timelog")
timelog_size = os.stat(timelog_filename)
msg = MIMEText("wrote " + account_filename + " (" + str(account_size.st_size) + " bytes)\nwrote " + timelog_filename + " (" + str(timelog_size.st_size) + " bytpes)")
msg['Subject'] = 'Payroll Nanny backup report for ' + date.today().isoformat()
msg['From'] = 'my_app_address'
msg['To'] = 'my_email_address'
s = SMTP()
s.sendmail('my_app_address', 'my_email_address', msg.as_string())