This is what Josh describe on how you can use SlyDial to save the day: "One rung down from having a friend call you to get out of a bad date is SlyDial, a new service that lets you send people voice mail messages without actually having to call them. Yes such a feature exists if someone legitimately leaves you a voice mail (giving you the option to leave a voice mail reply), but SlyDial lets you skip that first step by simply sending them the message as you would an SMS message. It's tricky, it's evil--I love it." Josh also mentioned that SlyDial is planning service plans for software application that can connect to your mobile phone's contact list, read his full review here.
[blogged with my Treo 750v]