Reference: https://docs.aws.amazon.com/cli/latest/reference/cloudwatch/put-metric-alarm.html

===HIGH CPU===
aws cloudwatch put-metric-alarm --alarm-name "High CPU Util on INSTANCE" --alarm-description "Alarm when CPU exceeds 90 percent" --metric-name CPUUtilization --namespace AWS/EC2 --statistic Average --period 300 --threshold 90 --comparison-operator GreaterThanThreshold  --dimensions "Name=InstanceId,Value=INSTANCE" --evaluation-periods 2 --alarm-actions "arn:aws:sns:REGION:ACCOUNT:SNSTOPIC" --unit Percent

===HIGH MEM===
aws cloudwatch put-metric-alarm --alarm-name "High Memory Util on INSTANCE" --alarm-description "Alarm when Memory exceeds 90 percent" --metric-name mem_used_percent --namespace AWS/EC2 --statistic Average --period 300 --threshold 90 --comparison-operator GreaterThanThreshold  --dimensions "Name=InstanceId,Value=INSTANCEID" --evaluation-periods 2 --alarm-actions "arn:aws:sns:REGION:ACCOUNT:SNSTOPIC" --unit Percent

===StatusCheckFailed===
aws cloudwatch put-metric-alarm --alarm-name "EC2 Status Check Failed --alarm-description "An EC2 Status Check Failed" --metric-name StatusCheckFailed --namespace AWS/EC2 --statistic Maximum --period 60 --unit Count --evaluation-periods 2 --threshold 1 --comparison-operator GreaterThanOrEqualToThreshold --dimensions "Name=InstanceID,Value=INSTANCEID" --treat-missing-data missing --alarm-actions "arn:aws:sns:REGION:ACCOUNT:SNSTOPIC"

===SystemStatusCheckFailed===
aws cloudwatch put-metric-alarm --alarm-name "System Status Check Failed" --alarm-description "An EC2 System Status Check Failed" --metric-name StatusCheckFailed_System --namespace AWS/EC2 --statistic Maximum --period 60 --unit Count --evaluation-periods 2 --threshold 1 --comparison-operator GreaterThanOrEqualToThreshold --dimensions "Name=InstanceID,Value=INSTANCEID" --treat-missing-data missing --alarm-actions "arn:aws:sns:REGION:ACCOUNT:SNSTOPIC"