I use Leeo Leeo Smart Alert Smoke/CO - $29.15 to connect make my hardwired smoke detctors integrate with Smartthings via IFTTT.
I used the [RELEASE] Universal Virtual Device Type and Translator to create a switch with the Smoke attribute. When Leeo detects an alarm, it triggers IFTTT to turn my Smartthings “Smoke Switch”. Smartthings treats it as a smoke device and will integrate it with Smart Home Monitor.