I've done some research at it appears there is currently not a way to RESTfully, or anyway to invoke a function to have Alexa make an announcement.
Could everyone please upvote this on the uservoice forum? - https://alexa.uservoice.com/forums/906892-alexa-skills-developer-voice-and-vote/suggestions/40613512-rest-api-that-can-send-an-alexa-announcement
I have a super simple lambda function that is invoked from an AWS IoT button that I use for my 94 year old mother in law. Currently it sends a text message and I know to go check on her. Ideally I would like the lambda function to also send an announcement to ALL my Alexa devices in the house that simply says, "Check on mom" ..... Not a Notification, where I have to notice the blue ring and ask it to play my notifications.
I've already accomplished the Notification using the Notify Me skill.