I am pretty sure the send email function of FM will only send email.
There are plugins and webviewer options for SMS.
I've used skype with links...
There must be a way....surely!!!???
@Andrew D are you reading this? Do you know?
There's a great utility app I learned about at Pause in Error called Alert Flag. You can download it for free at the App Store. The you can schedule notifications for your iOS device from FileMaker.
On the desktop I would stick to email.
And don't forget that you can add an fmserver email to your VIP on your device and then you will get a pop-up notification.
SMS is also a great way to do it.
You could use AppleScript to send an iMessage notification probably but I don't see the need for it, really and it would only work on the desktop.
Hope this helps.