I realize this would require some hefty additions to up.time, but it would be nice to be able to get an alert via email and acknowledge that alert by replying to the email rather than having to get to a computer, open a browser, login, and acknowledge the alert via the web interface.
Obviously it would be best to get to a computer in order to actually address the problem of which the alert is notifying, but for those issues that are known to be non-critical, this feature would be great.