Marco of Intellibits let me know that they have just released SmsScheduler. This is a simple application that lets you schedule SMS to be delivered at a later date. I wish RIM would include this natively for email and SMS but this is a great solution if you need it now.
From the product description:
Never forget to send an important SMS again! Messages with wishes, reminders for colleagues and friends, you name it…
With SmsScheduler you can prepare your SMS messages in advance, and schedule them for automatic delivery at any date & time in the future. Various types of recurrence are also supported, so that a Happy Birthday message is sent all years on Feb 12, for example.
* Allows to schedule unlimited SMS messages
* Allows to specify multiple recipient numbers for each scheduled SMS
* Recipient numbers are easily chosen from the device’s Address Book
* Supports daily, weekly, monthy and yearly recurrence
* All delivered messages are logged and listed through a Log screen
* Scheduler can be temporarily disabled
* Autostarts when the device is turned on, and then runs in background
* Very clean and simple user interface
* Very small size, just 22 KB
* Detailed on-screen instructions
* Works on all devices with OS 4.2 and newer
* Free updates for ever! (including new minor and major releases)