Last Updated Dec 12, 2008 1:51 PM EST
Fortunately, alternatives exist. For the moment, I can think of no better substitute than PingMe, which doesn't offer natural-language recognition (yet -- it's in the works) but does offer Sandy-like features. Like the latter, PingMe is a free service that sends you reminders using one or more methods.
Just create a "ping," set the details, then choose your desired reminder-delivery options (e-mail, SMS, Twitter, etc.). Your best bet is to use the PingMe site to set up your pings, but you can do it remotely, Sandy-style, via e-mail or Twitter. The only trick is remembering PingMe's necessary syntax.
To help you with that, the developers have created a "Welcome, Sandy users" tutorial that's quite informative. Meanwhile, check out Dial2Do, the voice-activated messaging service we're loving more and more. It supports PingMe!