It should certainly be doable. SmartThings ™ itself is not reliable enough for life and death applications like smoke alerts, but you could use some of the ideas in the following thread, just choose a more reliable platform.
On the other hand, since that thread was created there are now some simpler solutions on the market.
As you mentioned, there are already several bedshaker products on the market that can respond to a UL listed smoke alarm. One of those would probably be safest.
With regard to the alerts from the security system, I think I myself would be most likely to sleep wearing a smart watch that could vibrate when the text/email was received from the security system. That would be a very easy, very reliable solution.