Teach 2.5 year old what to do in an emergency

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My anxiety sometimes gets the best of me, and I found myself worrying what would happen if I became unconcious and it was only my 2 year old at home. I'm not so worried about myself as I am about him getting help without me. Do you think it best to teach him to dial 911 on my mobile, or go to the backyard and yell "Help 911" until someone comes? We really should get a landline so he knows where a phone is at all times. Thoughts?