There's a new software app called DoNotDisturb that will automatically send an SMS text message whenever you miss a
call. Sure, their call will get picked up by voicemail anyway, but the idea here is that you can let whoever called
know that you've received their call and will be calling them back as soon as you can or that you're in a meeting and
that they need to try again in a few hours (or if you're going to be that way, you can let people know that you
probably aren't going to be calling them back anytime soon). You can also set it so that only some numbers get
an auto-reply while others don't, or associate specific messages with specific numbers. Only available for Windows
Mobile-powered Pocket PC Phones for now, though a Smartphone version is on the way.