Hello,
If there is a need and it can be useful for the community, yes.
But the trigger should not impact performances, so it should be a one time trigger with the list of elements which will be processed and has been processed (onBefore / onAfter).
Best would be to not perform time consuming tasks during these triggers to not cause a timeout (PHP max execution time).
For your SMS case, I'm not even sure that the trigger will help you a lot, except if you want to send a SMS in the same time than the email ; but then you can use the HikaShop email trigger.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.